Mercury 300R HD CMS Mechanical Maintance Manual

Operation

and

Maintenance

Manual

© 2018 Mercury Marine

300R HD CMS Mechanical

8M0140585 518 eng

eng

Welcome

You have selected one of the finest marine power packages available. It
incorporates numerous design features to ensure operating ease and durability.

With proper care and maintenance, you will enjoy using this product for many
boating seasons. To ensure maximum performance and carefree use, we ask
that you thoroughly read this manual.

The Operation and Maintenance Manual contains specific instructions for using
and maintaining your product. We suggest that this manual remain with the
product for ready reference whenever you are on the water.

Thank you for purchasing one of our products. We sincerely hope your boating
will be pleasant!

Mercury Marine, Fond du Lac, Wisconsin, U.S.A.

Name / function:

John Pfeifer, President,
Mercury Marine

Read This Manual Thoroughly

IMPORTANT: If you do not understand any portion of this manual, contact your
dealer. Your dealer can also provide a demonstration of actual starting and
operating procedures.

Notice

Throughout this publication, and on your power package, warnings, cautions,

and notices, accompanied by the International Hazard Symbol

!

, may be
used to alert the installer and user to special instructions concerning a
particular service or operation that may be hazardous if performed incorrectly
or carelessly. Observe them carefully.

These safety alerts alone cannot eliminate the hazards that they signal. Strict
compliance with these special instructions while performing the service, plus
common sense operation, are major accident prevention measures.

!

WARNING

Indicates a hazardous situation which, if not avoided, could result in death or
serious injury.

!

CAUTION

Indicates a hazardous situation which, if not avoided, could result in minor or
moderate injury.

eng i

NOTICE

Indicates a situation which, if not avoided, could result in engine or major
component failure.

IMPORTANT: Identifies information essential to the successful completion of
the task.

NOTE: Indicates information that helps in the understanding of a particular step
or action.

IMPORTANT: The operator (driver) is responsible for the correct and safe
operation of the boat, the equipment aboard, and the safety of all occupants
aboard. We strongly recommend that the operator read this Operation and
Maintenance Manual and thoroughly understand the operational instructions for
the power package and all related accessories before the boat is used.

California Proposition 65

WARNING: This product can expose you to chemicals including
gasoline engine exhaust, which is known to the State of
California to cause cancer and birth defects or other
reproductive harm. For more information go to

www.P65Warnings.ca.gov.

The serial numbers are the manufacturer’s keys to numerous engineering
details that apply to your Mercury Marine power package. When contacting
Mercury Marine about service, always specify model and serial numbers.

Descriptions and specifications contained herein were in effect at the time this
was approved for printing. Mercury Marine, whose policies are based on
continuous improvement, reserves the right to discontinue models at any time
or to change specifications or designs without notice and without incurring
obligation.

Warranty Message

The product you have purchased comes with a limited warranty from Mercury
Marine; the terms of the warranty are set forth in the Warranty Manual included
with the product. The Warranty Manual contains a description of what is
covered, what is not covered, the duration of coverage, how to best obtain
warranty coverage, important disclaimers and limitations of damages, and
other related information. Please review this important information.

Mercury Marine products are designed and manufactured to comply with our
own high quality standards, applicable industry standards and regulations, as
well as certain emissions regulations. At Mercury Marine every engine is
operated and tested before it is boxed for shipment to make sure that the
product is ready for use. In addition, certain Mercury Marine products are
tested in a controlled and monitored environment, for up to 10 hours of engine
run time, in order to verify and make a record of compliance with applicable
standards and regulations. All Mercury Marine product, sold as new, receives
the applicable limited warranty coverage, whether the engine participated in
one of the test programs described above or not.

ii eng

Copyright and Trademark Information

© MERCURY MARINE. All rights reserved. Reproduction in whole or in
part without permission is prohibited.

Alpha, Axius, Bravo One, Bravo Two, Bravo Three, GO BOLDLY., Circle M with
Waves Logo, K‑planes, Mariner, MerCathode, MerCruiser, Mercury, Mercury
with Waves Logo, Mercury Marine, Mercury Precision Parts, Mercury
Propellers, Mercury Racing, MotorGuide, OptiMax, Quicksilver, SeaCore,
Skyhook, SmartCraft, Sport‑Jet, Verado, VesselView, Zero Effort, Zeus, #1 On
the Water and We're Driven to Win are registered trademarks of Brunswick
Corporation. Pro XS is a trademark of Brunswick Corporation. Mercury Product
Protection is a registered service mark of Brunswick Corporation.

Identification Records

Please record the following applicable information:

Outboard

Engine Model and Horsepower

Engine Serial Number

Gear Ratio

Propeller Number Pitch Diameter

Watercraft Identification Number (WIN) or Hull
Identification Number (HIN)

Purchase Date

Boat Manufacturer Boat Model Length

Exhaust Gas Emissions Certification Number (Europe Only)

eng iii

eng iv

General Information

Boater's Responsibilities..................................................................................... 1

Before Operating Your Outboard........................................................................ 1

Boat Horsepower Capacity................................................................................. 1

High‑Speed and High‑Performance Boat Operation.......................................... 2

Propeller Selection..............................................................................................2

Outboard Remote Control Models ..................................................................... 4

Lanyard Stop Switch........................................................................................... 5

Protecting People in the Water........................................................................... 7

Passenger Safety Message ‑ Pontoon Boats and Deck Boats...........................8

Wave and Wake Jumping................................................................................... 9

Impact with Underwater Hazards......................................................................10

Exhaust Emissions........................................................................................... 11

Selecting Accessories for Your Outboard......................................................... 13

Safe Boating Recommendations...................................................................... 13

Recording Serial Number................................................................................. 16

Specifications—300R HD................................................................................. 17

Component Identification.................................................................................. 19

Gearcase Identification..................................................................................... 20

Transporting

Trailering Boat/Outboard.................................................................................. 21

Fuel and Oil

Fuel Requirements........................................................................................... 22

Fuel Additives................................................................................................... 23

Low Permeation Fuel Hose Requirement ........................................................ 23

Fuel Demand Valve (FDV) Requirement.......................................................... 23

Engine Oil Recommendations—Race (R) Models............................................ 24

Checking and Adding Engine Oil...................................................................... 24

Features and Controls

Adaptive Speed Control.................................................................................... 28

Remote Control Features................................................................................. 28

Warning System............................................................................................... 28

Power Trim and Tilt...........................................................................................31

eng v

Operation

Important Daily Inspection Before Each Use ................................................... 36

Prestarting Check List.......................................................................................36

Operating in Freezing Temperatures................................................................ 36

Operating in Saltwater or Polluted Water......................................................... 37

Operating at High Elevations............................................................................ 37

Effects of Elevation and Weather on Performance........................................... 37

Setting Trim Angle while Running Engine at Idle Speed.................................. 38

Engine Break‑in Procedure...............................................................................39

Fuel Supply Module Priming Procedure........................................................... 39

Starting the Engine........................................................................................... 41

Gear Shifting..................................................................................................... 44

Stopping the Engine......................................................................................... 45

Maintenance

Cleaning Care Recommendations.................................................................... 46

EPA Emissions Regulations............................................................................. 48

Inspection and Maintenance Schedule............................................................. 49

300R HD Models Maintenance Schedule Decal............................................... 51

Flushing the Cooling System............................................................................ 52

Top Cowl Removal and Installation.................................................................. 52

Battery Inspection ............................................................................................ 54

Battery Cables and Clean Power Harness....................................................... 55

Fuel System...................................................................................................... 57

Corrosion Control Anode.................................................................................. 59

Propeller Replacement—31.75 mm (1‑1/4 in.) Diameter Propeller Shaft......... 60

Spark Plug Inspection and Replacement..........................................................61

Fuses................................................................................................................ 64

Alternator Drive Belt .........................................................................................66

Lubrication Points............................................................................................. 66

Trim Thrust Guide Wear Pad............................................................................ 68

Checking Power Trim Fluid (Single‑Ram Trim)................................................ 69

Checking Hydraulic Steering Fluid....................................................................70

Checking Power Steering Fluid........................................................................ 70

Changing Engine Oil and Filter......................................................................... 71

Checking Engine Oil Level................................................................................76

Exhaust Water Strainer Inspection................................................................... 77

Gearcase Lubricant.......................................................................................... 78

vi eng

Storage

Storage Preparation..........................................................................................81

Protecting External Outboard Components...................................................... 81

Protecting Internal Engine Components........................................................... 82

Gearcase.......................................................................................................... 82

Positioning Outboard for Storage..................................................................... 82

Battery Storage................................................................................................. 82

Troubleshooting

Starter Motor Will Not Crank the Engine........................................................... 83

Engine Will Not Start.........................................................................................83

Engine Runs Erratically.................................................................................... 83

Performance Loss.............................................................................................84

Battery Will Not Hold Charge............................................................................ 84

Owner Service Assistance

Service Assistance........................................................................................... 85

Ordering Literature............................................................................................87

Maintenance Log

Maintenance Log.............................................................................................. 89

eng vii

eng viii

Boater's Responsibilities

The operator (driver) is responsible for the correct and safe operation of the
boat and the safety of its occupants and general public. It is strongly
recommended that each operator read and understand this entire manual
before operating the outboard.

Be sure that at least one additional person onboard is instructed in the basics
of starting and operating the outboard and boat handling in case the driver is
unable to operate the boat.

Before Operating Your Outboard

Read this manual carefully. Learn how to operate your outboard properly. If you
have any questions, contact your dealer.

Safety and operating information that is practiced, along with using good
common sense, can help prevent personal injury and product damage.

This manual as well as safety labels posted on the outboard use the following
safety alerts to draw your attention to special safety instructions that should be
followed.

!

WARNING

Indicates a hazardous situation which, if not avoided, could result in death or
serious injury.

!

CAUTION

Indicates a hazardous situation which, if not avoided, could result in minor or
moderate injury.

NOTICE

Indicates a situation which, if not avoided, could result in engine or major
component failure.

Boat Horsepower Capacity

!

WARNING

Exceeding the boat's maximum horsepower rating can cause serious injury
or death. Overpowering the boat can affect boat control and flotation
characteristics or break the transom. Do not install an engine that exceeds
the boat's maximum power rating.

GENERAL INFORMATION

eng 1

Do not overpower or overload your boat. Most boats will carry a required
capacity plate indicating the maximum acceptable power and load as
determined by the manufacturer following certain federal guidelines. If in doubt,
contact your dealer or the boat manufacturer.

U.S. COAST GUARD CAP ACITY

MAXIMUM HORSEPOWER XXX

MAXIMUM PERSON
CAPACITY (POUNDS)

XXX

MAXIMUM WEIGHT
CAPACITY XXX

26777

High‑Speed and High‑Performance Boat Operation

If your outboard is to be used on a high‑speed or high‑performance boat with
which you are unfamiliar, we recommend that you do not operate it at its high
speed capability without first requesting an initial orientation and familiarization
demonstration ride with your dealer or an operator experienced with your boat/
outboard combination. For additional information, obtain a copy of our
Hi‑Performance Boat Operation booklet from your dealer, distributor, or
Mercury Marine.

Propeller Selection

The propeller on your outboard is one of the most important components in the
propulsion system. An improper propeller choice can significantly affect the
performance of your boat and could result in damage to the outboard engine.

When choosing a propeller, a full selection of aluminum and stainless steel
propellers specifically designed for your outboard are available through
Mercury Marine. To view the entire product offering and find the correct
propeller that is best suited for your application, visit
www.mercmarinepropellers.com or see your local authorized Mercury dealer.

SELECTING THE CORRECT PROPELLER

An accurate tachometer for measuring engine speed is important in choosing
the correct propeller.

Choose a propeller for your boating application that will allow the engine to
operate within the specified full throttle operating range. When operating the
boat at full throttle under normal load conditions, the engine RPM should be in
the upper half of the recommended full throttle RPM range. Refer to
Specifications. If engine RPM is above that range, select a propeller of
increased pitch in order to reduce engine RPM. If engine RPM is below the
recommended range, select a propeller of reduced pitch to increase engine
RPM.

GENERAL INFORMATION

2 eng

IMPORTANT: To ensure proper fit, and performance, Mercury Marine
recommends the use of Mercury or Quicksilver branded propellers and
mounting hardware.

Propellers are designated by the diameter, pitch, number of blades, and
material. The diameter and pitch are stamped (cast) into the side or the end of
the propeller hub. The first number represents the diameter of the propeller and
the second number represents the pitch. For example, 14x19 represents a
propeller with a 14 inch diameter and 19 inches of pitch.

a - Diameter
b - Pitch ‑ Travel during one revolution

The following are some propeller basics that will help you determine the correct
propeller for your boating application.

Diameter ‑ The diameter is the distance across the imaginary circle that is
made when the propeller rotates. The correct diameter for each propeller has
been predetermined for the design of your outboard. However, when more than
one diameter is available for the same pitch, use a larger diameter for heavy
boat applications and a smaller diameter for lighter applications.

Pitch ‑ The pitch is the theoretical distance, in inches, that a propeller travels
forward during one revolution. Pitch can be thought of similar to gears in a car.
The lower the gear, the faster the car will accelerate, but with lower overall top
speed. Likewise, a lower pitch propeller will accelerate quickly, but top‑end
speed will be reduced. The higher the propeller pitch the faster the boat will
usually go; though typically slowing acceleration.

Determining the correct pitch size ‑ First, check the full throttle RPM under
normal load condition. If the full throttle RPM is within the recommended range,
select a replacement or upgrade propeller with the same pitch as the current
propeller.

• Adding 1 inch of pitch will reduce the full throttle RPM by 150 to 200

• Subtracting 1 inch of pitch will increase full throttle RPM by 150 to 200

a

b

22669

GENERAL INFORMATION

eng 3

• Upgrading from a 3‑blade propeller to a 4‑blade propeller will generally
decrease full throttle RPM by 50 to 100

IMPORTANT: Avoid damage to the engine. Never use a propeller that allows
the engine to exceed the recommended full throttle RPM range when under
normal full throttle operation.

PROPELLER MATERIAL

Most propellers manufactured by Mercury Marine are made from either
aluminum or stainless steel. Aluminum is suitable for general purpose use and
is standard equipment on many new boats. Stainless steel is over five times
more durable than aluminum and typically provides performance gains in
acceleration and top end speed due to design efficiencies. Stainless steel
propellers also come in a larger variety of sizes and styles that allow you to dial
in the ultimate performance for your boat.

3 BLADE VS. 4 BLADE

Available in many sizes of both aluminum and stainless, 3 and 4‑blade
propellers have unique performance characteristics. In general, 3‑blade
propellers offer good all around performance and higher top speed than
4‑blade propellers. However, 4‑blade propellers are usually faster to plane and
more efficient at cruising speeds, but lack the top end speed of a 3‑blade
propeller.

Outboard Remote Control Models

The remote control connected to your outboard must be equipped with a start
in neutral only protection device. This prevents the engine from starting when
the shift is actuated in any position other than neutral.

!

WARNING

Starting the engine with the drive in gear can cause serious injury or death.
Never operate a boat that does not have a neutral‑safety‑protection device.

N

58237

GENERAL INFORMATION

4 eng

Lanyard Stop Switch

The purpose of a lanyard stop switch is to turn off the engine when the operator
moves far enough away from the operator's position (as in accidental ejection
from the operator's position) to activate the switch. Tiller handle outboards and
some remote control units are equipped with a lanyard stop switch. A lanyard
stop switch can be installed as an accessory ‑ generally on the dashboard or
side adjacent to the operator's position.

A decal near the lanyard stop switch is a visual reminder for the operator to
attach the lanyard to their personal flotation device (PFD) or wrist.

The lanyard cord is usually 122–152 cm (4–5 feet) in length when stretched out,
with an element on one end made to be inserted into the switch and a clip on
the other end for attaching to the operator's PFD or wrist. The lanyard is coiled
to make its at‑rest condition as short as possible to minimize the likelihood of
lanyard entanglement with nearby objects. Its stretched‑out length is made to
minimize the likelihood of accidental activation should the operator choose to
move around in an area close to the normal operator's position. If it is desired
to have a shorter lanyard, wrap the lanyard around the operator's wrist or leg,
or tie a knot in the lanyard.

a - Lanyard cord clip
b - Lanyard decal
c - Lanyard stop switch

Read the following Safety Information before proceeding.

c

a

b

53910

OFF

RUN

ATTACH LANYARD

GENERAL INFORMATION

eng 5

Important Safety Information: The purpose of a lanyard stop switch is to stop
the engine when the operator moves far enough away from the operator's
position to activate the switch. This would occur if the operator accidentally falls
overboard or moves within the boat a sufficient distance from the operator's
position. Falling overboard and accidental ejections are more likely to occur in
certain types of boats such as low sided inflatables, bass boats, high
performance boats, and light, sensitive handling fishing boats operated by a
hand tiller. Falling overboard and accidental ejections are also likely to occur as
a result of poor operating practices such as sitting on the back of the seat or
gunwale at planing speeds, standing at planing speeds, sitting on elevated
fishing boat decks, operating at planing speeds in shallow or obstacle infested
waters, releasing your grip on a steering wheel or tiller handle that is pulling in
one direction, drinking alcohol or consuming drugs, or daring high speed boat
maneuvers.

While activation of the lanyard stop switch will stop the engine immediately, a
boat will continue to coast for some distance depending upon the velocity and
degree of any turn at shut down. However, the boat will not complete a full
circle. While the boat is coasting, it can cause injury to anyone in the boat's
path as seriously as the boat would when under power.

We strongly recommend that other occupants be instructed on proper starting
and operating procedures should they be required to operate the engine in an
emergency (if the operator is accidentally ejected).

!

WARNING

If the operator falls out of the boat, stop the engine immediately to reduce the
possibility of serious injury or death from being struck by the boat. Always
properly connect the operator to the stop switch using a lanyard.

!

WARNING

Avoid serious injury or death from deceleration forces resulting from
accidental or unintended stop switch activation. The boat operator should
never leave the operator's station without first disconnecting the stop switch
lanyard from the operator.

Accidental or unintended activation of the switch during normal operation is
also a possibility. This could cause any, or all, of the following potentially
hazardous situations:

• Occupants could be thrown forward due to unexpected loss of forward
motion ‑ a particular concern for passengers in the front of the boat who
could be ejected over the bow and possibly struck by the gearcase or
propeller.

• Loss of power and directional control in heavy seas, strong current, or
high winds.

• Loss of control when docking.

GENERAL INFORMATION

6 eng

KEEP THE LANYARD STOP SWITCH AND LANYARD CORD IN GOOD
OPERATING CONDITION

Before each use, check to ensure the lanyard stop switch works properly. Start
the engine and stop it by pulling the lanyard cord. If the engine does not stop,
have the switch repaired before operating the boat.

Before each use, visually inspect the lanyard cord to ensure it is in good
working condition and that there are no breaks, cuts, or wear to the cord.
Check that the clips on the ends of the cord are in good condition. Replace any
damaged or worn lanyard cords.

Protecting People in the Water

WHILE YOU ARE CRUISING

It is very difficult for a person standing or floating in the water to take quick
action to avoid a boat heading in his/her direction, even at slow speed.

21604

Always slow down and exercise extreme caution any time you are boating in an
area where there might be people in the water.

Whenever a boat is moving (coasting) and the outboard gear shift is in neutral
position, there is sufficient force by the water on the propeller to cause the
propeller to rotate. This neutral propeller rotation can cause serious injury.

WHILE THE BOAT IS STATIONARY

!

WARNING

A spinning propeller, a moving boat, or any solid device attached to the boat
can cause serious injury or death to swimmers. Stop the engine immediately
whenever anyone in the water is near your boat.

Shift the outboard into neutral and shut off the engine before allowing people to
swim or be in the water near your boat.

GENERAL INFORMATION

eng 7

Passenger Safety Message ‑ Pontoon Boats and Deck Boats

Whenever the boat is in motion, observe the location of all passengers. Do not
allow any passengers to stand or use seats other than those designated for
traveling faster than idle speed. A sudden reduction in boat speed, such as
plunging into a large wave or wake, a sudden throttle reduction, or a sharp
change of boat direction, could throw them over the front of the boat. Falling
over the front of the boat between the two pontoons will position them to be run
over by the outboard.

BOATS HAVING AN OPEN FRONT DECK

No one should ever be on the deck in front of the fence while the boat is in
motion. Keep all passengers behind the front fence or enclosure.

Persons on the front deck could easily be thrown overboard or persons
dangling their feet over the front edge could get their legs caught by a wave
and pulled into the water.

26782

!

WARNING

Sitting or standing in an area of the boat not designed for passengers at
speeds above idle can cause serious injury or death. Stay back from the front
end of deck boats or raised platforms and remain seated while the boat is in
motion.

BOATS WITH FRONT MOUNTED, RAISED PEDESTAL FISHING SEATS

Elevated fishing seats are not intended for use when the boat is traveling faster
than idle or trolling speed. Sit only in seats designated for traveling at faster
speeds.

GENERAL INFORMATION

8 eng

Any unexpected, sudden reduction in boat speed could result in the elevated
passenger falling over the front of the boat.

26783

Wave and Wake Jumping

Operating recreational boats over waves and wake is a natural part of boating.
However, when this activity is done with sufficient speed to force the boat hull
partially or completely out of the water, certain hazards arise, particularly when
the boat enters the water.

26784

The primary concern is the boat changing direction while in the midst of the
jump. In such case, the landing may cause the boat to veer violently in a new
direction. Such a sharp change in direction can cause occupants to be thrown
out of their seats, or out of the boat.

!

WARNING

Wave or wake jumping can cause serious injury or death from occupants
being thrown within or out of the boat. Avoid wave or wake jumping whenever
possible.

There is another less common hazardous result from allowing your boat to
launch off a wave or wake. If the bow of your boat pitches down far enough
while airborne, upon water contact it may penetrate under the water surface
and submarine for an instant. This will bring the boat to a nearly instantaneous
stop and can send the occupants flying forward. The boat may also steer
sharply to one side.

GENERAL INFORMATION

eng 9

Impact with Underwater Hazards

Your outboard is equipped with a hydraulic trim and tilt system that also
contains a shock absorbing feature. This feature helps the outboard withstand
damage in the case of impact with an underwater object at low to moderate
speeds. At higher speeds, the force of the impact may exceed the system’s
ability to absorb the energy of the impact and cause serious product damage.

No impact protection exists while in reverse. Use extreme caution when
operating in reverse to avoid striking underwater objects.

Reduce speed and proceed with caution whenever you drive a boat in shallow
water areas or in areas where you suspect underwater obstacles may exist that
could be struck by the outboard or the boat bottom. The most significant

action you can take to help reduce injury or impact damage from striking
a floating or underwater object is to control the boat speed. Under these
conditions, boat speed should be kept to the minimum planing speed,
typically 24 to 40 km/h (15 to 25 mph).

26785

!

WARNING

Avoid serious injury or death from all or part of an outboard or drive unit
coming into the boat after striking a floating or underwater object. When
operating in waters where objects may be at the surface or just under the
surface of the water, reduce your speed and keep a vigilant lookout.

Examples of objects that can cause engine damage are dredging pipes,
bridge supports, wing dams, trees, stumps, and rocks.

Striking a floating or underwater object could result in any of an infinite number
of situations. Some of these situations could yield the following:

• Part of the outboard or the entire outboard could break loose and fly into
the boat.

• The boat could move suddenly in a new direction. A sharp change in
direction can cause occupants to be thrown out of their seats or out of the
boat.

• The boat's speed could rapidly reduce. This will cause occupants to be
thrown forward or even out of the boat.

GENERAL INFORMATION

10 eng

• The outboard or boat could sustain impact damage.

After striking a submerged object, stop the engine as soon as possible and
inspect it for any broken or loose parts. If damage is present or suspected, the
outboard should be taken to an authorized dealer for a thorough inspection and
necessary repair.

The boat should also be checked for any hull fractures, transom fractures, or
water leaks. If water leaks are discovered after an impact, immediately activate
the bilge pump.

Operating a damaged outboard could cause additional damage to other parts
of the outboard or could affect control of the boat. If continued running is
necessary, do so at greatly reduced speeds.

!

WARNING

Operating a boat or engine with impact damage can result in product
damage, serious injury, or death. If the vessel experiences any form of
impact, have an authorized Mercury Marine dealer inspect and repair the
vessel or power package.

Exhaust Emissions

BE ALERT TO CARBON MONOXIDE POISONING

Carbon monoxide (CO) is a deadly gas that is present in the exhaust fumes of
all internal combustion engines, including the engines that propel boats, and
the generators that power boat accessories. By itself, CO is odorless, colorless,
and tasteless, but if you can smell or taste engine exhaust, you are inhaling
CO.

Early symptoms of carbon monoxide poisoning, which are similar to the
symptoms of seasickness and intoxication, include headache, dizziness,
drowsiness, and nausea.

!

WARNING

Inhaling engine exhaust gases can result in carbon monoxide poisoning,
which can lead to unconsciousness, brain damage, or death. Avoid exposure
to carbon monoxide.

Stay clear from exhaust areas when engine is running. Keep the boat
well‑ventilated while at rest or underway.

GENERAL INFORMATION

eng 11

STAY CLEAR OF EXHAUST AREAS

41127

co

co

co

co

co

co

co

co

co

co

co

co

co

co

co

co

co

co

co

co

Engine exhaust gases contain harmful carbon monoxide. Avoid areas of
concentrated engine exhaust gases. When engines are running, keep
swimmers away from the boat, and do not sit, lie, or stand on swim platforms or
boarding ladders. While underway, do not allow passengers to be positioned
immediately behind the boat (platform dragging, teak/body surfing). This
dangerous practice not only places a person in an area of high engine exhaust
concentration, but also subjects them to the possibility of injury from the boat
propeller.

GOOD VENTILATION

Ventilate the passenger area, open side curtains or forward hatches to remove
fumes.

Example of desired air flow through the boat:

POOR VENTILATION

Under certain running and/or wind conditions, permanently enclosed or canvas
enclosed cabins or cockpits with insufficient ventilation may draw in carbon
monoxide. Install one or more carbon monoxide detectors in your boat.

Although the occurrence is rare, on a very calm day, swimmers and
passengers in an open area of a stationary boat that contains, or is near, a
running engine may be exposed to a hazardous level of carbon monoxide.

GENERAL INFORMATION

12 eng

1. Examples of poor ventilation while the boat is stationary:

a - Operating the engine when the boat is moored in a confined space
b - Mooring close to another boat that has its engine operating

2. Examples of poor ventilation while the boat is moving:

a - Operating the boat with the trim angle of the bow too high
b - Operating the boat with no forward hatches open (station wagon effect)

Selecting Accessories for Your Outboard

Genuine Mercury Precision or Quicksilver Accessories have been specifically
designed and tested for your outboard. These accessories are available from
Mercury Marine dealers.

IMPORTANT: Check with your dealer before installing accessories. The misuse
of approved accessories or the use of nonapproved accessories can damage
the product.

Some accessories not manufactured or sold by Mercury Marine are not
designed to be safely used with your power package and may void warranty.
Acquire and read the installation and operation manuals for each selected
accessory.

Safe Boating Recommendations

To safely enjoy the waterways, familiarize yourself with local and all other
governmental boating regulations and restrictions and consider the following
suggestions.

Know and obey all nautical rules and laws of the waterways.

21626

a

b

a

b

21628

GENERAL INFORMATION

eng 13

• We recommend that all powerboat operators complete a boating safety
course. In the U.S., the U.S. Coast Guard Auxiliary, the Power Squadron,
the Red Cross, and your state or provincial boating law enforcement
agency provide courses. For more information in the U.S., call the Boat
U.S. Foundation at 1‑800‑336‑BOAT (2628).

Perform safety checks and required maintenance.

• Follow a regular schedule and ensure that all repairs are properly made.

Check safety equipment onboard.

• Here are some suggestions of the types of safety equipment to carry
when boating:

Approved fire extinguishers

Signal devices: flashlight, rockets or flares, flag, and whistle or horn

Tools necessary for minor repairs

Anchor and extra anchor line

Manual bilge pump and extra drain plugs

Drinking water

Radio

Paddle or oar

Spare propeller, thrust hubs, and an appropriate wrench

First aid kit and instructions

Waterproof storage containers

Spare operating equipment, batteries, bulbs, and fuses

Compass and map or chart of the area

Personal flotation device (one per person onboard)

Watch for signs of weather change and avoid foul weather and rough‑sea
boating.

Tell someone where you are going and when you expect to return.

Passenger boarding.

• Stop the engine whenever passengers are boarding, unloading, or are
near the back (stern) of the boat. Shifting the drive unit into neutral is not
sufficient.

Use personal flotation devices.

• Federal law requires that there be a U.S. Coast Guard‑approved life
jacket (personal flotation device), correctly sized and readily accessible
for every person onboard, plus a throwable cushion or ring. We strongly
advise that everyone wear a life jacket at all times while in the boat.

Prepare other boat operators.

GENERAL INFORMATION

14 eng

• Instruct at least one person onboard in the basics of starting and
operating the engine and boat handling in case the driver becomes
disabled or falls overboard.

Do not overload your boat.

• Most boats are rated and certified for maximum load (weight) capacities
(refer to your boat's capacity plate). Know your boat's operating and
loading limitations. Know if your boat will float if it is full of water. When in
doubt, contact your authorized Mercury Marine dealer or the boat
manufacturer.

Ensure that everyone in the boat is properly seated.

• Do not allow anyone to sit or ride on any part of the boat that was not
intended for such use. This includes the backs of seats, gunwales,
transom, bow, decks, raised fishing seats, and any rotating fishing seat.
Passengers should not sit or ride anywhere that sudden unexpected
acceleration, sudden stopping, unexpected loss of boat control, or sudden
boat movement could cause a person to be thrown overboard or into the
boat. Ensure that all passengers have a proper seat and are in it before
any boat movement.

Never operate a boat while under the influence of alcohol or drugs. It is
the law.

• Alcohol or drugs can impair your judgment and greatly reduce your ability
to react quickly.

Know your boating area and avoid hazardous locations.

Be alert.

• The operator of the boat is responsible by law to maintain a proper
lookout by sight and hearing. The operator must have an unobstructed
view particularly to the front. No passengers, load, or fishing seats should
block the operator's view when the boat is above idle or planing transition
speed. Watch out for others, the water, and your wake.

Never drive your boat directly behind a water‑skier.

• Your boat traveling at 40 km/h (25 mph) will overtake a fallen skier who is
61 m (200 ft) in front of you in five seconds.

Watch fallen skiers.

• When using your boat for waterskiing or similar activities, always keep a
fallen or down skier on the operator's side of the boat while returning to
attend to the skier. The operator should always have the down skier in
sight and never back up to the skier or anyone in the water.

Report accidents.

GENERAL INFORMATION

eng 15

• Boat operators are required by law to file a boating accident report with
their state boating law enforcement agency when their boat is involved in
certain boating accidents. A boating accident must be reported if 1) there
is loss of life or probable loss of life, 2) there is personal injury requiring
medical treatment beyond first aid, 3) there is damage to boats or other
property where the damage value exceeds $500.00, or 4) there is
complete loss of the boat. Seek further assistance from local law
enforcement.

Recording Serial Number

It is important to record this number for future reference. The serial number is
located on the outboard, as shown.

a - Model designation
b - Serial number
c - Certified Europe insignia (as applicable)

a

XXXXXXXXX

XXXXXXXX

XXXX

c

b

66301

GENERAL INFORMATION

16 eng

Specifications—300R HD

300R HD MODELS

Attribute 300R HD
Horsepower 300
Kilowatts 221
Full throttle RPM range 5800–6400
Idle RPM in neutral gear* 600
Idle charge compensation** 600–725
Troll control RPM limit 550–1000
Number of cylinders 8

Displacement

4.6 Liter

4,576 cc (279.2 cid)
Cylinder bore 92 mm (3.62 in.)
Stroke 86 mm (3.38 in.)
Spark plug NGK LKAR7C‑9
Spark plug gap 0.9 mm (0.035 in.)
Spark plug hex size 14 mm
Sport Master ratio 1.75:1
137 mm (5.4 in.) ratio 1.75:1

Gearcase
capacity

Sport Master
RH, LH

620 mL (21.0 fl oz)

137 mm (5.4
in.) RH

720 mL (24.4 fl oz)

137 mm (5.4
in.) LH

680 mL (23.0 fl oz)

Recommended gasoline

Refer to Fuel and Oil

Recommended oil

Refer to Fuel and Oil

Engine oil capacity with oil
filter replacement

6.6 Liter (7.0 US qt)

Required battery type 12‑volt absorbed glass mat (AGM) battery

Battery
type***

USA (SAE)

800 minimum marine cranking amps (MCA)

with a minimum reserve capacity of 135

RC25 rating

International
(EN)

975 minimum cold cranking amps (CCA) with

a minimum 65 amp hour (Ah)

GENERAL INFORMATION

eng 17

*Engine at normal operation temperature.
**The idle charge compensation may automatically increase the engine speed

up to 725 RPM to compensate for a low battery charge condition. The
increased idle RPM will charge the battery at a higher rate. Activating troll
control (optional accessory) will override the idle charge compensation
feature.

***Battery manufacturers may rate and test their batteries to different
standards. MCA, CCA, Ah, and reserve capacity (RC) are the ratings
recognized by Mercury Marine. Manufacturers that use standards different
than these, such as equivalent MCA, do not meet Mercury Marine battery
requirements.

GENERAL INFORMATION

18 eng

Component Identification

a - Service access door
b - Top cowl
c - Engine flush
d - Auxiliary tilt switch
e - Cooling water intake holes
f - External steering bracket (dealer installed option or factory installation

available)

g - Water pump indicator hole
h - Engine oil drain
i - Exhaust relief

a

b

c

d

f

g

h

i

e

66302

GENERAL INFORMATION

eng 19

Gearcase Identification

Diameter

or Type

Identification

Features

Illustration

137 mm
(5.4 in.)

Water intake—

eight per side,

four torpedo low

water

L

L

64308

Left‑hand rotation

gearcase—LL
stamped on the
end of propeller

shaft

Sport
Master

Water intake—

three torpedo low

water

64532

L

L

Left‑hand rotation

gearcase—LL
stamped on the
end of propeller

shaft

GENERAL INFORMATION

20 eng

Trailering Boat/Outboard

The best position to trailer your boat is with the outboard tilted down in a
vertical operating position.

If additional ground clearance is required, the outboard should be tilted up
using an accessory outboard support device. Refer to your local dealer for
recommendations. Additional clearance may be required for railroad crossings,
driveways, and trailer bouncing.

66304

IMPORTANT: Do not rely on the power trim/tilt system to maintain proper
ground clearance for trailering. The power trim/tilt system is not intended to
support the outboard during transport trailering.

Shift the outboard into reverse gear. This prevents the propeller from spinning.

TRANSPORTING

eng 21

Fuel Requirements

IMPORTANT: Use of improper gasoline can damage your engine. Engine
damage resulting from the use of improper gasoline is considered misuse
of the engine and will not be covered under the limited warranty.

FUEL RATINGS

Mercury outboard engines will operate satisfactorily with any major brand of
unleaded gasoline that meets the following specifications:

USA and Canada ‑ A posted pump octane rating of 87 (R+M)/2, minimum, for
most models. Premium gasoline 91 (R+M)/2 octane is also acceptable for most
models. Do not use leaded gasoline.

Outside USA and Canada ‑ A posted pump octane rating of 91 RON,
minimum, for most models. Premium gasoline (95 RON) is also acceptable for
all models. Do not use leaded gasoline.

USING REFORMULATED (OXYGENATED) GASOLINE (USA ONLY)

Reformulated gasoline is required in certain areas of the USA and is
acceptable for use in your Mercury Marine engine. The only oxygenate
currently in use in the USA is alcohol (ethanol, methanol, or butanol).

GASOLINE CONTAINING ALCOHOL

Bu16 Butanol Fuel Blends

Fuel blends of up to 16.1% butanol (Bu16) that meet the published Mercury
Marine fuel rating requirements are an acceptable substitute for unleaded
gasoline. Contact your boat manufacturer for specific recommendations on
your boat's fuel system components (fuel tanks, fuel lines, and fittings).

Methanol and Ethanol Fuel Blends

IMPORTANT: The fuel system components on your Mercury Marine engine will
withstand up to 10% alcohol (methanol or ethanol) content in the gasoline. Your
boat's fuel system may not be capable of withstanding the same percentage of
alcohol. Contact your boat manufacturer for specific recommendations on your
boat's fuel system components (fuel tanks, fuel lines, and fittings).

Be aware that gasoline containing methanol or ethanol may cause increased:

• Corrosion of metal parts

• Deterioration of rubber or plastic parts

• Fuel permeation through the rubber fuel lines

• Likelihood of phase separation (water and alcohol separating from the
gasoline in the fuel tank)

FUEL AND OIL

22 eng

!

WARNING

Fuel leakage is a fire or explosion hazard, which can cause serious injury or
death. Periodically inspect all fuel system components for leaks, softening,
hardening, swelling, or corrosion, particularly after storage. Any sign of
leakage or deterioration requires replacement before further engine
operation.

IMPORTANT: If you use gasoline that contains or might contain methanol or
ethanol, you must increase the frequency of inspection for leaks and
abnormalities.

IMPORTANT: When operating a Mercury Marine engine on gasoline containing
methanol or ethanol, do not store the gasoline in the fuel tank for long periods.
Cars normally consume these blended fuels before they can absorb enough
moisture to cause trouble; boats often sit idle long enough for phase separation
to take place. Internal corrosion may occur during storage if alcohol has
washed protective oil films from internal components.

Fuel Additives

To minimize carbon deposit buildup in the engine, it is recommended to add
Mercury or Quicksilver Quickstor fuel stabilizer additive to the engine's fuel at
each tank fill throughout the boating season. Use additive as directed on
container.

Low Permeation Fuel Hose Requirement

Required for outboards manufactured for sale, sold, or offered for sale in the
United States.

• The Environmental Protection Agency (EPA) requires that any outboard
manufactured after January 1, 2009, must use low permeation fuel hose
for the primary fuel hose connecting the fuel tank to the outboard.

• Low permeation hose is USCG Type B1‑15 or Type A1‑15, defined as not
exceeding 15 g/m²/24 h with CE 10 fuel at 23 °C as specified in SAE J
1527 ‑ marine fuel hose.

Fuel Demand Valve (FDV) Requirement

Whenever a pressurized fuel tank is used, a fuel demand valve is required to
be installed in the fuel hose between the fuel tank and the engine. The fuel
demand valve prevents pressurized fuel from entering the engine and causing
a fuel system overflow or possible fuel spillage.

FUEL AND OIL

eng 23

The fuel demand valve has a manual release. The manual release can be used
(pushed in) to open (bypass) the valve in case of a fuel blockage in the valve.

a - Fuel demand valve ‑ installed in the

fuel hose between the fuel tank and

the engine

b - Manual release
c - Vent/water drain holes

Engine Oil Recommendations—Race (R) Models

Mercury or Quicksilver NMMA FC‑W or NMMA FC‑W catalyst compatible
certified SAE 10W‑30 Marine 4‑Stroke Engine Oil is recommended for general
all‑temperature use. As an optional choice, Mercury or Quicksilver SAE
25W‑40 Mineral Marine 4‑Stroke Engine Oil or SAE 25W‑40 Synthetic Blend
Marine 4‑Stroke engine oil may be used. If the recommended Mercury or
Quicksilver NMMA FC‑W certified oils are not available, a major outboard
manufacturer's brand of NMMA FC‑W certified 4‑Stroke outboard oil of similar
viscosity may be used.

IMPORTANT: The use of nondetergent oils, multiviscosity oils (other than
Mercury or Quicksilver NMMA FC‑W certified oil or a major brand NMMA FC‑W
certified oil), full synthetic oils, low quality oils, or oils that contain solid additives
are not recommended.

Engine Oil

C

+100

+80
+60
+40
+20

0

+38
+27
+16
+4

-7

-18

F

+120

+49

10W-30

64064

6.6 L (7.0 U.S. qt)

Checking and Adding Engine Oil

IMPORTANT: Inspect oil for signs of contamination. Oil contaminated with
water will have a milky color to it; oil contaminated with fuel will have a strong
fuel smell. If contaminated oil is noticed, have the engine checked by your
dealer.

a

c

b

46453

FUEL AND OIL

24 eng

IMPORTANT: Do not overfill. Tilt the outboard out/up past vertical for
approximately one minute to allow trapped oil to drain back to the oil sump. The
outboard must be in a vertical (not tilted) position when checking the engine oil.
For accurate readings, check the oil only when the engine is cold or after the
engine has not run for at least an hour.

1. Before starting a cold engine, tilt the outboard out/up past vertical to allow
trapped oil to drain back to the oil sump. Allow the outboard to remain
tilted for approximately one minute.

2. Tilt the outboard to a vertical operating position.

3. Push down on the port side of the service access door to unlock and open
the door.

64230

Push here to unlock

NOTE: On the underside of the service access door is a quick reference decal
which lists the type of oil to use on various products.

64634

Quick reference decal

FUEL AND OIL

eng 25

4. Remove the dipstick and observe the area of the five beads.

a - Service access door
b - Oil fill cap
c - Dipstick

5. The bead or crosshatch which shows oil furthest from the end is the oil
level.

65509

Oil level example

NOTE: New oil (level) may be difficult to identify which is why the crosshatch
between the beads are part of the dipstick assembly. When checking the oil
level, if oil is on any of the five oil range beads or four crosshatch, the oil level
is within the safe operating range. When the oil level is only on the lowest oil
range bead, the operator can add 1.8 Liter (2 US qt) of oil and the level will
remain within the safe operating range. When the oil becomes dark from hours
of product use, it will be easier to identify the oil level on the dipstick.

b

c

a

63305

FUEL AND OIL

26 eng

IMPORTANT: Repeated removal and insertion of the dipstick will
subsequently deposit oil further up the dipstick tube which potentially may
cause an error reading the oil level.

a - Safe operating range
b - General area after an oil change
c - Add 1.8 Liter (2 US qt) of oil

6. If none of the beads shows the oil level, remove the oil filler cap and add

1.8 Liter (2 US qt) of the specified outboard motor oil.

7. Allow a few minutes for the oil to drain into the sump and insert the oil
dipstick.

8. Remove the dipstick and inspect if the oil level is within the safe operating
range.

9. Install the dipstick and oil filler cap hand‑tight.

10. Close the service access door and lock into place by pushing on the port
side of the door.

c

a

b

65510

FUEL AND OIL

eng 27

Adaptive Speed Control

This outboard package utilizes adaptive speed control which automatically
adjusts the engine load (throttle) to maintain engine speed (RPM). For
example, when the boat operator steers into a hard turn, which results in
increased load on the engine and a loss of RPM, the propulsion control module
(PCM) will open the throttle to maintain RPM through the turn, without the need
for the operator to increase the remote control throttle handle. Another example
is when cruising or utilizing the boat for tow sports, engine speed will remain
constant, regardless of load changes due to waves, trim position, turning or
load changes from tow sports. Adaptive speed control is active from idle RPM
up to max rated RPM, however, can only maintain engine speed when the
throttle is less than wide open.

Remote Control Features

Your boat may be equipped with one of the Mercury Precision or Quicksilver
remote controls shown. If not, consult your dealer for a description of the
functions and operations of the remote control.

a -

Trim/tilt switch – Refer to Power Trim and Tilt

b - Ignition key switch – OFF, ON, START
c -

Throttle only button – Refer to Operation – Starting the Engine

d - Safety lanyard switch

Warning System

WARNING HORN SIGNALS

When the key switch is turned to the ON position, the horn will turn on for a
moment as a test to indicate the horn is working.

There are two types of warning horns to alert the operator of an active problem
within the engine’s operating system.

aa

a

b

c

c

c

58240

d

FEATURES AND CONTROLS

28 eng

1.

Continuous six second beep: Indicates a critical engine condition.
Depending on the condition, the Engine Guardian system may engage
and protect the engine by limiting power. You should return to port
immediately and contact your servicing dealer.

2.

Intermittent short beeps for six seconds: Indicates a noncritical engine
condition. This condition does not require immediate attention. You may
continue using your boat, however, depending on the nature of the
problem, the engine’s power may be limited by the Engine Guardian
system. Refer to Engine Guardian System. You should contact your
servicing dealer at your earliest convenience.

It is important to note that in either of the above scenarios, the horn will only
sound one time. If you key the engine off and restart it, the horn will sound
again, one time, if the fault is still present. For visual display of the specific
engine functions and additional engine data, refer to SmartCraft Product
information, following.

A few of the noncritical conditions indicated by the intermittent short beeps for
six seconds can be corrected by the operator. These operator correctable
conditions are as follows:

•

Water in the engine mounted fuel filter. Refer to Maintenance ‑
Low‑Pressure Fuel Filter.

• Cooling system (water pressure or engine temperature) problem. Stop the
engine and check the water intake holes in the lower unit for obstruction.

•

Low engine oil level. Refer to Fuel and Oil ‑ Checking and Adding
Engine Oil.

ENGINE GUARDIAN SYSTEM

The Engine Guardian system monitors the critical sensors on the engine for
any early indications of problems. Engine Guardian is functional whenever your
engine is operating, so you never have to be concerned about whether or not
you are protected. The system will respond to a problem by sounding the
warning horn for six seconds and/or reducing engine power in order to provide
engine protection.

If Engine Guardian has been activated, reduce the engine speed. The problem
will need to be identified and corrected. The system must be reset before the
engine will operate at higher speeds. Moving the throttle lever back to the idle
position will reset the Engine Guardian system. If the Engine Guardian system
has determined the reset has not corrected the problem, Engine Guardian will
remain activated, limiting the throttle. The problem must be identified and
corrected before Engine Guardian will allow the engine to reach a normal
operating RPM.

FEATURES AND CONTROLS

eng 29

OVERSPEED REV LIMIT

The overspeed rev limit is set at an RPM greater than the operating range. In
the event that the engine is operated at an RPM greater than or equal to the
overspeed limit, the PCM does not allow the engine to maintain the power
requested by the operator. Refer to General Information ‑ Specification to
determine this engine’s RPM limit.

Upon reaching the beginning of the overspeed rev limit, Engine Guardian will
cut fuel to one bank of cylinders. If the operator does not reduce engine speed,
Engine Guardian will cut the fuel to all cylinders until the engine speed has
dropped below the rev limit. There is no audible warning while Engine Guardian
overspeed limit is active.

SMARTCRAFT PRODUCT

A Mercury SmartCraft System instrument package can be purchased for this
outboard. A few of the functions the instrument package will display are engine
RPM, coolant temperature, oil pressure, water pressure, battery voltage, fuel
consumption, and engine operating hours.

The SmartCraft instrument package will also aid in Engine Guardian
diagnostics. The SmartCraft instrument package will display critical engine
alarm data and potential problems.

EXHAUST GAS OVER TEMPERATURE

When the Engine Guardian system detects the exhaust gas temperature is high
(fault code 2124‑20), the warning horn will beep and the engine RPM will be
limited. SmartCraft gauges which have the ability display text, will alert the
operator with a short text, long text, and the action which the operator should
follow. This Guardian warning and engine power reduction can possibly be
corrected by inspecting the gear housing water inlet for blockage and the
exhaust water strainer for blockage. Refer to Maintenance ‑ Exhaust Water
Strainer Inspection.

SmartCraft Displayed Text

Short text Critical ‑ Overtemp

Long text Engine exhaust manifold is overheating

Action

Stop engine and check for plugged exhaust water strainer. If

condition persists return to port immediately. Service engine

before next use.

1. Stop the engine.

2. Check the gear housing water inlet for blockage.

3.

Check the exhaust water strainer for blockage. Refer to Maintenance ‑
Exhaust Water Strainer Inspection.

4. If there is no blockage and the condition persists, return to port
immediately.

FEATURES AND CONTROLS

30 eng

LOSS OF SHIFT COMMAND

When the Engine Guardian system detects a loss of shift control (fault code
339‑23), the warning horn will beep and the engine RPM will be limited.
SmartCraft gauges which have the ability to display text will alert the operator
with a short text, long text, and the action which the operator should follow.

SmartCraft Displayed Text

Short text Reverse Gear Unavailable

Long text

Reverse gear is not available. Moving control lever into reverse will

result in a forward gear shift. Engine power is limited.

Action Return to port immediately ‑ Service engine before next use.

IMPORTANT: Engine Guardian loss of shift command will only allow the engine
to be shifted into forward or neutral; access to reverse gear is not possible.

Operation of the outboard will be extremely limited when the Engine Guardian
system detects a loss of shift control fault. The outboard will only shift from
neutral to forward after the remote control handle is advanced to approximately
the mid‑throttle position. Engine RPM will not increase until after forward gear
engagement. The throttle will be limited to approximately 1000 RPM to allow
emergency boat operation. If the remote control shift handle is moved from
neutral into reverse, the lower unit will shift into forward gear.

Power Trim and Tilt

The outboard has a trim/tilt control called power trim. This enables the operator
to easily adjust the position of the outboard by pressing the trim switch. Moving
the outboard in closer to the boat transom is called trimming in or down. Moving
the outboard further away from the boat transom is called trimming out or up.
The term trim generally refers to the adjustment of the outboard within the first
20° range of travel. This is the range used while operating the boat on plane.
The term tilt is generally used when referring to adjusting the outboard further
up out of the water. The outboard can be tilted up past the trim range for
shallow water operation or loading the boat onto a trailer. With the engine
turned off and ignition switch turned on, the outboard can be tilted out of the
water.

• Below 2000 RPM the engine can be trimmed or tilted to any range.
Caution is advised when operating the engine past the tilt range. Ensure
the water pickups are submerged.

• While in the trim range and the engine is above 2000 RPM, you can only
trim to the maximum trim range.

• If the engine is below 2000 RPM and is in the trailer range, advancing the
throttle will allow the engine to achieve a maximum RPM of 4250. Engine
operation in this capacity (above the normal 2000 limit) should only be
used for loading or unloading the boat onto or off the trailer. It should not
be used during normal boat operation.

FEATURES AND CONTROLS

eng 31

NOTE: Exceeding 4250 RPMs the engine PCM will begin Engine Guardian
protection.

a - Trim switch
b - Tilt range
c - Trim range

POWER TRIM OPERATION

With most boats, operating around the middle of the trim range will give
satisfactory results. However, to take full advantage of the trimming capability
there may be times when you choose to trim your outboard all the way in or
out. Along with an improvement in some performance aspects comes a greater
responsibility for the operator, and this is being aware of some potential control
hazards.

The most significant control hazard is a pull or torque that can be felt on the
steering wheel or tiller handle. This steering torque results from the outboard
being trimmed so the propeller shaft is not parallel to the water surface.

!

WARNING

Trimming the outboard beyond a neutral steering condition may result in a
pull on the steering wheel or tiller handle and loss of boat control. Maintain
control of the boat if trimming beyond a neutral steering condition.

Consider the following lists carefully.

1. Trimming in or down can:

• Lower the bow

• Result in quicker planing off, especially with a heavy load or a stern
heavy boat

• Generally improve the ride in choppy water

a

UP
DN

c

b

63388

FEATURES AND CONTROLS

32 eng

• Increase steering torque or pull to the right (with the normal right‑hand
rotation propeller)

• In excess, can lower the bow of some boats to a point where they
begin to plow with their bow in the water while on plane. This can
result in an unexpected turn in either direction (called bow steering or
oversteering) if any turn is attempted, or if a significant wave is
encountered.

2. Trimming out or up can:

• Lift the bow higher out of the water

• Generally increase top speed

• Increase clearance over submerged objects or a shallow bottom

• Increase steering torque or pull to the left at a normal installation
height (with the normal right‑hand rotation propeller)

• In excess, can cause boat porpoising (bouncing) or propeller
ventilation

• Cause engine overheating if any cooling water intake holes are above
the waterline

AUXILIARY TILT SWITCH

This switch can be used to tilt the outboard up or down using the power trim
system.

a - Auxiliary tilt switch

a

47704

FEATURES AND CONTROLS

eng 33

TRIM LIMIT PIN (SINGLE-RAM TRIM)

!

WARNING

Operating the boat at high speeds with the outboard trimmed too far under
can create excessive bow steer, resulting in the operator losing control of the
boat. Install the trim limit pin in a position that prevents excessive trim under
and operate the boat in a safe manner.

Starboard side shown—port side

similar

a - Adjustment holes
b - Nut
c - Trim limit pin

A trim limit pin, secured with a nut, is included on both sides of the heavy‑duty
swivel bracket. The location of this pin will determine how far down the
outboard can be trimmed. Three adjustment holes are present on each transom
bracket to adjust the trim limit.

1. Remove the nut from the trim limit pin on both sides of the heavy‑duty
swivel bracket.

2. Remove the pins from and install them into the desired adjustment holes.

3. Install and tighten the nuts.

OPERATING IN SHALLOW WATER

When operating your boat in shallow water, you can tilt the outboard beyond
the maximum trim range to prevent hitting bottom.

1. Reduce the engine speed below 2000 RPM.

2. Tilt the outboard up. Make sure all the cooling water intake holes stay
submerged at all times.

• Below 2000 RPM the engine can be trimmed or tilted to any range.
Caution is advised when operating the engine past the tilt range. Ensure
the water pickups are submerged.

• If the engine is below 2000 RPM and is in the trailer range, advancing the
throttle will allow the engine to achieve a maximum RPM of 4250. Engine
operation in this capacity (above the normal 2000 limit) should only be
used for loading or unloading the boat onto or off the trailer. It should not
be used during normal boat operation.

66779

a

b

c

FEATURES AND CONTROLS

34 eng

NOTE: Exceeding 4250 RPMs the engine PCM will begin Engine Guardian
protection.

FEATURES AND CONTROLS

eng 35

Important Daily Inspection Before Each Use

Any outboard mounted on the boat must have the mounting hardware
inspected and checked to ensure that the hardware has not become loose. A
decal on the transom bracket reminds the owner to check the fasteners
securing the outboard to the transom before each use.

51985

Decal on the transom bracket

Prestarting Check List

• Operator knows safe navigation, boating, and operating procedures.

• An approved personal flotation device of suitable size for each person
aboard and readily accessible (it is the law).

• A ring type life buoy or buoyant cushion designed to be thrown to a
person in the water.

• Know your boats' maximum load capacity. Look at the boat capacity plate.

• Fuel supply OK.

• Arrange passengers and load in the boat so the weight is distributed
evenly and everyone is seated in a proper seat.

• Tell someone where you are going and when you expect to return.

• It is illegal to operate a boat while under the influence of alcohol or drugs.

• Know the waters and area you will be boating; tides, currents, sand bars,
rocks, and other hazards.

•

Make inspection checks listed in Maintenance ‑ Inspection and

Maintenance Schedule.

Operating in Freezing Temperatures

If there is a chance of ice forming on the water, the outboard should be
removed and drained completely of water. If ice should form at any level inside
the outboard driveshaft housing between the water pump and the powerhead, it
will block cooling water flow to the engine which may cause possible damage.

OPERATION

36 eng

If the boat cannot be removed from the water during freezing temperatures, the
outboard should be tilted up so the trailing edge of the antiventilation plate is
protruding slightly above the water surface—refer to the following graphic
illustration. At this tilt angle, the engine’s water pump and cooling water
passages are best protected from freezing up with ice.

0

66308

Operating in Saltwater or Polluted Water

We recommend that you flush the internal water passages of your outboard
with fresh water after each use in salt or polluted water. This will prevent a
buildup of deposits from clogging the water passages. Refer to Maintenance ‑
Flushing the Cooling System.

If you keep your boat moored in the water, always tilt the outboard so the
gearcase is completely out of water (except in freezing temperatures) when not
in use.

Wash the outboard exterior and flush out the exhaust outlet of the propeller and
gearcase with fresh water after each use. Each month, spray Mercury Precision
or Quicksilver Corrosion Guard on external metal surfaces. Do not spray on
corrosion control anodes as this will reduce the effectiveness of the anodes.

Operating at High Elevations

Your engine automatically compensates for high elevation changes. A different
pitch propeller may help reduce some normal performance loss resulting from
reduced oxygen in the air. Consult your dealer.

Effects of Elevation and Weather on Performance

The following conditions lower engine performance and cannot be
compensated by the engine fuel or electronic management systems:

• Above sea level elevations

• High temperature

• Low barometric pressure

OPERATION

eng 37

• High humidity

These conditions above reduce air density to the engine, which in turn lowers
the following:

• Boost pressure on supercharged engines

• Horsepower and torque throughout the RPM range

• Peak RPM

• Cranking compression

EXAMPLE: An engine running at an elevation of 8,000 feet will have over a
30% power loss while a loss of engine power on a hot and humid day could be
as much as 14%. These losses apply to normally aspirated and supercharged
engines.

Compensating for power robbing conditions:

• Switch to lower pitch propeller.

• Change gear ratio.

Some boat performance can be improved by dropping to a lower pitch
propeller, but engine performance will still remain lower. In some cases, a gear
ratio reduction may be more beneficial. To optimize engine performance, prop
the engine to allow it to operate at or near the top end of the recommended
maximum RPM range at wide‑open throttle with a normal boat load.

Other advantages to propeller or gear ratio changes:

• Reduces the possibility of detonation

• Enhances overall reliability and durability of the engine

Setting Trim Angle while Running Engine at Idle Speed

The exhaust relief hole on the outboard can become submerged on some
boats if the engine is trimmed full in while running at idle speed. This may result
in exhaust restriction, rough idle, excessive smoke, and fouled spark plugs. If
this condition exists, trim outboard up until exhaust relief hole is out of the
water.

a - Relief hole submerged (wrong)
b - Relief hole above waterline (correct)

a

b

63389

OPERATION

38 eng

Engine Break‑in Procedure

IMPORTANT: Failure to follow the engine break‑in procedures can result in
poor performance throughout the life of the engine and can cause engine
damage. Always follow break‑in procedures.

1. For the first two hours of operation, run the engine at varied throttle
settings up to 4500 RPM or at three‑quarter throttle, and at full throttle for
approximately one minute every ten minutes.

2. For the next eight hours of operation, avoid continuous operation at full
throttle for more than five minutes at a time.

Fuel Supply Module Priming Procedure

The fuel supply module (FSM) is not vented to the ambient air. The air trapped
in the FSM, fuel lines, and fuel rail, will be slightly compressed during the initial
ignition key on with a dry or drained fuel system. Additional key on events
under these conditions, will not compress the air further to finish the priming of
the FSM. Excessive number of key on events may eventually damage the fuel
pumps. The volume of air trapped in the FSM must be purged to prime the fuel
system. This can be achieved by connecting a tool to the fuel rail Schrader
valve fitting to quickly purge the system into an approved container, or by
cranking the engine.

PRIMING THE FSM WITH A PURGE TOOL

The use of a purge tool for priming the FSM is the preferred method, but is not
always practical. The objective is to purge the air entrained in the fuel system
through a purge tool connected to the fuel rail Schrader valve test port. During
the key on, opening the dump valve will allow the air to be purged from the
FSM and fuel rail. This method should be used on vessels when the fuel
system leading to the outboard is restrictive; antisiphon valve or holds a
relatively large volume of fuel because of a long fuel supply line or a vessel
mounted water‑separating fuel filter is installed. If a primer bulb is installed, it
can be used during the priming event to shorten the amount of time required to
start the engine.

1. Verify the engine is in a level vertical position.

2. Verify the vessel fuel supply line is connected to the outboard fuel system
inlet fitting.

3. Connect a fuel pressure gauge to the fuel rail Schrader valve.

4. Secure the fuel pressure gauge purge hose into an appropriate fuel
container to collect excess fuel.

5. Open the fuel pressure gauge purge valve and turn the ignition key ON.
The fuel pumps will run for approximately five seconds.

6. Turn the ignition key OFF and then back ON. The fuel pumps will run for
approximately five seconds. Continue this ignition key cycle until the
purged fuel is relatively clear of air bubbles.

OPERATION

eng 39

NOTE: If the outboard fuel system does not prime within 15 key ON events,
check for leaks in the fuel supply line to the outboard. Repair as needed. If no
leak is found, the fuel supply system to the outboard may be too restrictive.
Correct the condition and try again.

7. Remove the fuel pressure gauge.

8. Turn the ignition key ON. When the fuel pumps stop running, start the
engine. The engine may not start on the first attempt. The engine will run
rough at idle for up to two minutes while the residual air is purged from the
fuel system.

PRIMING THE FSM (RAN OUT OF FUEL CONDITION)

The use of a purge tool for priming the FSM is the preferred method, but is not
always practical. When the vessel fuel system is void of fuel volume, it can be
primed without the use of a purge tool. The objective is to purge the air
entrained in the fuel system through the fuel injectors during engine cranking to
allow fuel to enter the fuel module. This method can be used on vessels where
the fuel inlet system to the outboard is less restrictive and holds a relatively
small volume of fuel; a short fuel supply line, no water‑separating fuel filter, or
water‑separating fuel filter is already primed. If a primer bulb is installed, it can
be used during the priming event to shorten the amount of time required to start
the engine.

NOTE: In most cases, the priming procedure can be accomplished by purging
the air from one fuel rail.

1. Verify the engine is in a level vertical position.

2. Verify the vessel fuel supply line is connected to the outboard fuel system
inlet fitting.

3. Turn the ignition key ON. The fuel pumps will run for approximately five
seconds.

4. Turn the ignition key to the START position and release the key. The
ECM controls the activation of the starter. The starter may continue
cranking for up to eight seconds.

NOTE: When priming a drained fuel system, residual fuel may cause the
engine to flare and stall which shortens the engine cranking event.

5. Continue with the ignition key ON and START sequence until the engine
continues to run.

IMPORTANT: Allow the starter motor to cool for 20 to 30 seconds between full
eight second crank events. Limit the number of events to a maximum of 10 full
eight second cranking events.

6. Once the engine starts, it may run rough at idle for up to two minutes
while the residual air is purged from the fuel system.

7. If the fuel system will not prime within 10 full eight second cranking
events, use the previous procedure Priming the FSM with a Purge Tool
to prime the fuel system.

OPERATION

40 eng

Starting the Engine

Before starting, read the Prestarting Check List, and Engine Break‑in
Procedure in this section.

NOTICE

Without sufficient cooling water, the engine, the water pump, and other
components will overheat and suffer damage. Provide a sufficient supply of
water to the water inlets during operation.

1. Push down on the port side of the service access door to unlock and open
the door.

64230

Push here to unlock

OPERATION

eng 41

2.

Check the engine oil level. Refer to Fuel and Oil ‑ Checking and Adding
Engine Oil.

a - Service access door
b - Oil fill cap
c - Dipstick

3. Ensure that the cooling water intake is submerged.

66310

b

c

a

63305

OPERATION

42 eng

4.

Set the lanyard stop switch to the RUN position. Refer to General
Information ‑ Lanyard Stop Switch.

19791

5. Shift the outboard to neutral (N) position.

N

58237

6. Ignition key starting ‑ Turn the ignition key to the START position and
release the key. The electronic starting system will automatically crank the
engine for starting. If the engine fails to start, the engine will stop
cranking. Turn the key to the START position again until the engine starts.

NOTE: For initial start of a new engine or for an engine that ran out of fuel or
was drained of fuel, the fuel system should be filled as follows:

Turn the ignition key switch to the ON position for approximately five seconds.
Turn the key to the START position and release it, the engine will crank for a
maximum of eight seconds. The engine may start, run rough, and stall while
filling the system. Repeat this starting procedure until the engine remains
running. Allow the starter motor to cool for 20–30 seconds between start
attempts.

19804

7. After the engine starts, check for a steady stream of water flowing out of
the water pump indicator hole.

OPERATION

eng 43

IMPORTANT: If no water is coming out of the water pump indicator hole, stop
the engine and check the cooling water intake for obstruction. No obstruction
may indicate a water pump failure or blockage in the cooling system. These
conditions will cause the engine to overheat. Have the outboard checked by
your dealer. Operating the engine while overheated will cause engine damage.

WARMING UP ENGINE

Before beginning operation, allow the engine to warm up at idling speed for
three minutes.

Gear Shifting

IMPORTANT: Observe the following:

•

Never shift the outboard into or out of gear unless the engine speed
is at idle. Shifting at higher than engine idle speed could cause
damage to the gearcase.

•

Do not shift the outboard into reverse when the forward motion of
the boat is greater than a no wake speed. Shifting into reverse at
higher boat speeds could cause the engine to stall, and in some
situations, this could cause water to be drawn into the cylinders,
resulting in severe engine damage.

•

Do not shift the outboard into reverse when the engine is not
running. Damage to the shift linkage could occur.

• The outboard has three gear shift positions: forward (F), neutral (N), and
reverse (R).

• When shifting, always stop at the neutral position and allow the engine
idle speed to stabilize before shifting into another gear.

• Always shift the outboard into gear with a quick motion.

• After shifting the outboard into gear, advance the lever further to increase
speed.

N

RF

58239

OPERATION

44 eng

Stopping the Engine

Reduce the engine speed and shift the outboard to neutral position. Turn the
ignition key to "OFF" position.

26843

OFF

ON

START

OPERATION

eng 45

Cleaning Care Recommendations

OUTBOARD CARE

To keep your outboard in the best operating condition, it is important that your
outboard receive the periodic inspections and maintenance listed in the
Inspection and Maintenance Schedule. We urge you to keep it maintained
properly to ensure the safety of you and your passengers, and retain its
dependability.

Record maintenance performed in the Maintenance Log at the back of this
book. Save all maintenance work orders and receipts.

Selecting Replacement Parts For Your Outboard

We recommend using original Mercury Precision or Quicksilver replacement
parts and Genuine Lubricants.

DO NOT USE CAUSTIC CLEANING CHEMICALS

IMPORTANT: Do not use caustic cleaning chemicals on the outboard power
package. Some cleaning products contain strong caustic agents such as hull
cleaners with hydrochloric acid. These cleaners can degrade some of the
components they come in contact with including critical steering fasteners.

Damage to steering fasteners may not be obvious during visual inspection and
this damage may lead to catastrophic failure. Some caustic cleaning chemicals
may cause or accelerate corrosion. Exercise caution when using cleaning
chemicals around the engine and follow the recommendations on the
packaging of the cleaning product.

CLEANING GAUGES

IMPORTANT: Never use high‑pressure water to clean gauges.
Routine cleaning of the gauges is recommended to prevent a buildup of salt

and other environmental debris. Crystalized salt can scratch the gauge display
lens when using a dry or damp cloth. Ensure that the cloth has a sufficient
amount of fresh water to dissolve and remove salt or mineral deposits. Do not
apply aggressive pressure on the display lens while cleaning.

When water marks cannot be removed with a damp cloth, mix a 50/50 solution
of warm water and isopropyl alcohol to clean the display lens. Do not use
acetone, mineral spirits, turpentine type solvents, or ammonia based cleaning
products. The use of strong solvents or detergents may damage the coating,
the plastics, or the rubber keys on the gauges. If the gauge has a sun cover
available, it is recommended that the cover be installed when the unit is not in
use to prevent UV damage to the plastic bezels and rubber keys.

CLEANING REMOTE CONTROLS

IMPORTANT: Never use high‑pressure water to clean remote controls.

MAINTENANCE

46 eng

Routine cleaning of the remote control external surfaces is recommended to
prevent a buildup of salt and other environmental debris. Use a cloth towel
which has a sufficient amount of fresh water to dissolve and remove salt or
mineral deposits.

When water marks cannot be removed with a damp cloth, mix a 50/50 solution
of warm water and isopropyl alcohol to clean the remote control. Do not use
acetone, mineral spirits, turpentine type solvents, or ammonia based cleaning
products. The use of strong solvents or detergents may damage the coating,
the plastics, or the rubber components on the remote control.

CLEANING CARE FOR TOP AND BOTTOM COWLS

IMPORTANT: Dry wiping (wiping the plastic surface when it is dry) will result in
minor surface scratches. Always wet the surface before cleaning. Do not use
detergents containing hydrochloric acid. Follow the cleaning and waxing
procedure.

Cleaning and Waxing Procedure

1. Before washing, rinse the cowls with clean water to remove dirt and dust
that may scratch the surface.

2. Wash the cowls with clean water and a mild nonabrasive soap. Use a soft
clean cloth when washing.

3. Dry thoroughly with a soft clean cloth.

4. Wax the surface using a nonabrasive automotive polish (polish designed
for clear coat finishes). Remove the applied wax by hand using a clean
soft cloth.

5. To remove minor scratches, use Mercury Marine Cowl Finishing
Compound (92‑859026K 1).

CLEANING CARE FOR THE POWERHEAD (SALTWATER USE)

If the outboard is operated in saltwater, remove the top cowl and flywheel
cover. Inspect the powerhead and powerhead components for salt buildup.
Wash off any salt buildup from the powerhead and powerhead components
with fresh water. Keep water spray out of the air filter/intake and alternator.
After washing, allow the powerhead and components to dry. Apply Quicksilver
or Mercury Precision Lubricants Corrosion Guard spray on the external metal
surfaces of the powerhead and powerhead components. Do not allow the
Corrosion Guard spray to come in contact with the alternator drive belt or belt
pulleys.

IMPORTANT: Do not allow lubricant or Corrosion Guard spray to come in
contact with the alternator drive belt or the belt pulleys. The alternator drive belt
could slip and be damaged if it becomes coated with any lubricant or Corrosion
Guard spray.

MAINTENANCE

eng 47

Tube Ref

No.

Description Where Used Part No.

120

Corrosion Guard

External metal surfaces of the powerhead

and powerhead components.

92-802878 55

EPA Emissions Regulations

All new outboards manufactured by Mercury Marine are certified to the United
States Environmental Protection Agency, as conforming to the requirements of
the regulations for the control of air pollution from new outboard motors. This
certification is contingent on certain adjustments set to factory standards. For
this reason, the factory procedure for servicing the product must be strictly
followed and, wherever practicable, returned to the original intent of the design.

Maintenance, replacement, or repair of the emission control devices and
systems may be performed by any marine spark ignition (SI) engine
repair establishment or individual.

EMISSION CERTIFICATION LABEL

An emission certification label, showing emission levels and engine
specifications directly related to emissions, is placed on the engine at the time
of manufacture.

a - Idle speed
b - Engine horsepower
c - Piston displacement
d - Engine power ‑ kilowatts
e - Date of manufacture
f - US EPA engine family name
g - Regulated emission limit for the engine family
h - Regulated emission limit for the engine family
i - Recommended spark plug and gap
j - Percent of fuel line permeation

OWNER RESPONSIBILITY

The owner/operator is required to have routine engine maintenance performed
to maintain emission levels within prescribed certification standards.

SPARK PLUG:

GAP:

EMISSION CONTROL
INFORMATION

THIS ENGINE CONFORMS TO
EMISSION REGULATIONS FOR SPARK IGNITION MARINE ENGINES

CALIFORNIA AND U.S. EPA

REFER TO OWNERS MANUAL FOR REQUIRED MAINTENANCE,
SPECIFICATIONS, AND ADJUSTMENTS

IDLE SPEED (in gear):

FAMILY:

HC+NOx:FEL:

LOW PERM/HIGH PERM:

g/kWh

hp

L

e

d

c

b

a

f

g

h

i

HC+NOx:FEL:

g/kWh

hp

L

CO FEL:

g/kWhkwg/kWh

j

43210

MAINTENANCE

48 eng

The owner/operator is not to modify the engine in any manner that would alter
the horsepower or allow emission levels to exceed their predetermined factory
specifications.

Inspection and Maintenance Schedule

BEFORE EACH USE

•

Check engine oil level. Refer to Checking Engine Oil Level.

• Check that the lanyard stop switch stops the engine.

• Inspect the outboard for tightness to the boat transom. If any looseness of
the outboard or mounting fasteners exist, tighten the outboard mounting
fasteners to the specified torque. When looking for signs of looseness,
look for loss of outboard transom bracket material or paint caused by
movement between the outboard mounting fasteners and the outboard
transom brackets. Also look for signs of movement between the outboard
transom brackets and the boat transom (lift plate/setback bracket).

Description

Nm lb‑in. lb‑ft

Outboard mounting locknuts and
bolts ‑ standard boat transom

75 – 55.3

Outboard mounting locknuts and
bolts ‑ metal lift plates and setback
brackets

122 – 90

• Visually inspect the fuel system for deterioration or leaks.

• Check the steering system for binding or loose components.

• Check the propeller blades for damage.

• Inspect the hydraulic steering fittings and hoses for leaks or damage, if
equipped.

• Inspect the hydraulic steering fluid level, if equipped.

AFTER EACH USE

• Flush out the outboard cooling system if operating in salt, polluted, or
muddy water. Refer to Flushing the Cooling System.

• Wash off all salt deposits and flush out the exhaust outlet of the propeller
and gearcase with fresh water if operating in saltwater.

• If operating in saltwater, inspect the powerhead and powerhead
components for salt buildup. Refer to Cleaning Care for the Powerhead
(Saltwater Use).

EVERY 100 HOURS OF USE OR ONCE YEARLY, WHICHEVER
OCCURS FIRST

•

Inspect the exhaust water strainer. Refer to Exhaust Water Strainer
Inspection.

MAINTENANCE

eng 49

• Change engine oil and replace the oil filter. The oil should be changed
more often when the engine is operated under adverse conditions, such
as extended trolling. Refer to Changing Engine Oil and Filter.

• Check the engine mounted water‑separating low‑pressure fuel filter for
water or contaminants. Replace the filter if required. Refer to Fuel
System.

• Check the boat mounted water‑separating fuel filter for the presence of
water or contaminants. Drain the water or replace the filter if required.

•

Remove the propeller and lubricate the propeller shaft. Refer to Propeller
Replacement.

• Inspect the thermostat visually for corrosion or a broken spring. Ensure
that the thermostat closes completely at room temperature—dealer
service.

• Check the outboard mounting fasteners that fasten the outboard to the
boat transom. Tighten the fasteners to the specified torque—dealer
service.

Description

Nm lb‑in. lb‑ft

Outboard mounting locknuts and
bolts ‑ standard boat transom

75 – 55.3

Outboard mounting locknuts and
bolts ‑ metal lift plates and setback
brackets

122 – 90

• Check corrosion control anodes. Check more frequently when used in
saltwater. Refer to Corrosion Control Anode.

•

Drain and replace gearcase lubricant. Refer to Gearcase Lubrication.

•

Inspect battery. Refer to Battery Inspection.

• Saltwater usage: Remove and inspect spark plugs for corrosion and
replace as necessary. Apply Anti‑Seize Compound only on threads of
spark plug prior to installation. Refer to Spark Plug Inspection and
Replacement.

Tube Ref

No.

Description Where Used Part No.

81

Anti-Seize
Compound

Spark plug threads 92-898101389

• Check tightness of bolts, nuts, and other fasteners—dealer service.

• Add Quickleen Engine and Fuel System Cleaner to the fuel tank.

Tube Ref

No.

Description Where Used Part No.

Quickleen Engine &
Fuel System
Cleaner

Fuel tank 8M0047931

MAINTENANCE

50 eng

• Check cowl seals to ensure seals are intact and not damaged.

• Check that the intake silencer is in place, if equipped.

• Check that the idle relief muffler is in place, if equipped.

• Check for loose hose clamps and rubber boots on the air intake
assembly, if equipped.

EVERY 300 HOURS OF USE OR THREE YEARS

•

Check power trim fluid. Refer to Checking Power Trim Fluid.

• Lubricate all lubrication points. Lubricate more frequently when used in
saltwater. Refer to Lubrication Points.

•

Replace water pump impeller—dealer service.

1.

• Lubricate the splines on the upper driveshaft—dealer service.

• Check wiring and connectors—dealer service.

•

Replace alternator drive belt. Refer to Alternator Drive Belt—dealer
service.

• Replace the spark plugs.

• Inspect the trim thrust guide wear pads.

BEFORE PERIODS OF STORAGE

•

Refer to Storage section.

300R HD Models Maintenance Schedule Decal

65585

1. Replace the water pump impeller more often if overheating occurs or reduced water pressure is noted.

MAINTENANCE

eng 51

Flushing the Cooling System

Flush the internal water passages of the outboard with fresh water after each
use in salt, polluted, or muddy water. This will help prevent a buildup of
deposits from clogging the internal water passages.

NOTE: The outboard can be tilted or in the vertical operating position during
flushing.

1. With the engine turned off, place the outboard in either the operating
position (vertical) or in a tilted position.

2. Remove the flush connector from the bottom cowl.

3. Remove the cover from the flush connector and thread a water hose into
the flush connector.

64241

4. Turn on the water tap (1/2 maximum) and let the water flush through the
cooling system for about 15 minutes.

5. When flushing is complete, turn off the water and disconnect the water
hose.

6. Install the cover on the flush connector. Place the flush connector back
into the bottom cowl.

Top Cowl Removal and Installation

NOTE: It is recommended to remove and install the cowl while standing inside
the boat.

REMOVAL

1. Tilt the outboard up so the top of the cowl is facing you.

MAINTENANCE

52 eng

2. Push down on the port side of the service access door to unlock and open
the door.

64230

Push here to unlock

3. Press on the red lock button and lift the handle.

a - Service access

door

b - Red lock button
c - Handle

b

c

a

63306

MAINTENANCE

eng 53

4. Push the handle towards the aft to lock the handle into the cowl lift
position.

63308

Handle locked in the lift position

5. With a firm grip on the handle, carefully lift the cowl off the engine.

INSTALLATION

1. With a firm grip on the handle, carefully lower the top cowl over the
engine.

2. Verify the cowl is correctly aligned by checking the cowl alignment guides
on the port and starboard side of the cowl. If there is misalignment, one
side of the cowl will have a gap that is larger than the other side.

NOTE: It may be necessary to slightly lift the larger gap side of the cowl to
correctly position the alignment guides.

3. Gently push down on the cowl.

4. Push the red lock button and pull the handle. Continue to push the handle
down into the locked position.

5. Close the service access door.

Battery Inspection

The battery should be inspected at periodic intervals to ensure proper engine
starting capability.

IMPORTANT: Read the safety and maintenance instructions which accompany
your battery.

1. Turn off the engine before servicing the battery.

2. Ensure the battery is secure against movement.

MAINTENANCE

54 eng

3. Battery cable terminals should be clean, tight, and correctly installed.
Positive to positive and negative to negative.

4. Ensure the battery is equipped with a nonconductive shield to prevent
accidental shorting of battery terminals.

Battery Cables and Clean Power Harness

The battery cable connections should be checked often for corrosion or loose
retaining hardware. Maintaining this electrical connection helps ensure the
engine operation and accessories functionality remains trouble‑free. The
engine starting battery cables and the clean power harness wires must be
secured to the engine starting battery with nuts. Wing nuts are not acceptable.
The clean power harness must be secured to one of the battery cables with a
cable tie or other type of secure fastener.

a - 14‑pin data harness
b - Clean power harness connector at engine
c - Clean power harness
d - Battery
e - Negative engine battery cable
f - Positive engine battery cable

If the clean power harness fuse is open, try to locate and correct the cause of
the overload. If the cause is not found, the fuse may open again. Remove the
clean power fuse and look at the silver band inside the fuse. If the band is
broken (open), replace the fuse with the same rating (5 amp) and type fuse.

cab

26984

def

MAINTENANCE

eng 55

IMPORTANT: An ATC fuse has the fuse element enclosed or sealed inside the
plastic housing. This type of fuse must be used for marine applications. Marine
applications are exposed to environments that may have the potential to
accumulate explosive vapors. ATO fuses have exposed elements and should
never be used in marine applications.

a - Nuts
b - Clean power harness
c - Cable tie
d - Good fuse
e - Open fuse

BATTERY CONNECTIONS

IMPORTANT: The engine electrical system is negative (–) ground.
When connecting the engine battery, hex nuts must be used to secure the

battery leads to the battery posts. Tighten the hex nuts to the specified torque.

Description

Nm lb‑in. lb‑ft

Battery hex nuts 13.5 120 –

ORDER OF CONNECTION

Connect the battery cables in the following order:

1. All jumpers between parallel, multiple battery packs

2. From the batteries to the positive (+) engine lead

3. From the batteries to the positive (+) clean power

4. From the batteries to the negative (–) engine lead

5. From the batteries to the negative (–) clean power

6. From the batteries or main ground (–) bus to the negative (–) starboard
helm main power relay

b

a

c

64518

d

e

MAINTENANCE

56 eng

Fuel System

!

WARNING

Fuel is flammable and explosive. Ensure that the key switch is off and the
lanyard is positioned so that the engine cannot start. Do not smoke or allow
sources of spark or open flame in the area while servicing. Keep the work
area well ventilated and avoid prolonged exposure to vapors. Always check
for leaks before attempting to start the engine, and wipe up any spilled fuel
immediately.

IMPORTANT: Use an approved container to collect and store fuel. Wipe up
spilled fuel immediately. Material used to contain spilled fuel must be disposed
of in an approved receptacle.

Before servicing any part of the fuel system:

1. Stop engine and disconnect the battery.

2. Perform fuel system service in a well‑ventilated area.

3. Inspect any completed service work for sign of fuel leakage.

FUEL LINE INSPECTION

Visually inspect the fuel line for cracks, swelling, leaks, hardness, or other signs
of deterioration or damage. If any of these conditions are found, the fuel line
must be replaced.

LOW-PRESSURE FUEL FILTER

The low‑pressure fuel filter can be serviced as a general maintenance item
when the water‑in‑fuel alarm is activated.

!

WARNING

Fuel is flammable and explosive. Ensure that the key switch is off and the
lanyard is positioned so that the engine cannot start. Do not smoke or allow
sources of spark or open flame in the area while servicing. Keep the work
area well ventilated and avoid prolonged exposure to vapors. Always check
for leaks before attempting to start the engine, and wipe up any spilled fuel
immediately.

Removal

IMPORTANT: Use an approved container to collect and store fuel. Wipe up
spilled fuel immediately. Material used to contain spilled fuel must be disposed
of in an approved container.

1. Verify the ignition key switch is in the OFF position and that the lanyard
switch is positioned so the engine cannot start.

2. Remove the top cowl.

3. Locate the fuel filter on the starboard aft side of the engine near the
bottom spark plug.

MAINTENANCE

eng 57

4. Push in on the fuel hose release tabs and disconnect the fuel hoses from
the fuel filter.

5. Disconnect the water‑in‑fuel sensor harness.

NOTE: If there is a boat mounted water‑separating fuel filter with a
water‑in‑fuel sensor installed, the sensor harness would be connected to the
boat mounted filter.

a - Fuel hose release tabs
b - Water‑in‑fuel sensor harness

6. Rotate the filter clockwise approximately 1/4 of a turn and lift the filter out.

63415

Filter rotated 1/4 turn

7. Empty the fuel filter contents into an approved container and dispose
according to local regulations.

a

b

63414

MAINTENANCE

58 eng

8. Wipe up any spilled fuel.

Installation

1. Apply a small amount of 2‑4‑C with PTFE to the fuel filter grommet.

63416

Tube Ref

No.

Description Where Used Part No.

95

2-4-C with PTFE Fuel filter grommet 92-802859A 1

2. Install the fuel filter and rotate counterclockwise 1/4 turn to retain the filter.

3. Connect the water‑in‑fuel sensor harness.

NOTE: If there is a boat mounted water‑separating fuel filter with a
water‑in‑fuel sensor installed, the sensor harness would be connected to the
boat mounted filter.

4. Connect the fuel hoses to the fuel filter securely with the locking hose
connections.

5. Turn the key to the RUN position and inspect for fuel leaks. Repair any
fuel leaks if necessary.

Corrosion Control Anode

The outboard has corrosion control anodes at different locations. An anode
helps protect the outboard against galvanic corrosion by sacrificing its metal to
be slowly eroded instead of the outboard metals.

Each anode requires periodic inspection, especially in saltwater which will
accelerate the erosion. To maintain this corrosion protection, always replace
the anode before it is 50% eroded. Never paint or apply a protective coating on
the anode as this will reduce effectiveness of the anode.

MAINTENANCE

eng 59

Two anodes are located on the engine; one anode is on the bottom of the
transom bracket assembly and the other is on the gear housing.

66327

Propeller Replacement—31.75 mm (1‑1/4 in.) Diameter Propeller
Shaft

!

WARNING

Rotating propellers can cause serious injury or death. Never operate the boat
out of the water with a propeller installed. Before installing or removing a
propeller, place the drive unit in neutral and engage the lanyard stop switch
to prevent the engine from starting. Place a block of wood between the
propeller blade and the anti‑ventilation plate.

1. Shift the outboard into neutral position.

2. Place a block of wood between the gearcase and the propeller to hold the
propeller and remove the propeller nut.

29592

3. Pull the propeller straight off the shaft. If the propeller is seized to the
shaft and cannot be removed, have the propeller removed by an
authorized dealer.

4. To aid in future removal of the propeller, liberally coat the propeller shaft
splines with one of the following Mercury/Quicksilver products:

MAINTENANCE

60 eng

Tube Ref

No.

Description Where Used Part No.

Extreme Grease Propeller shaft splines 8M0071842

95

2-4-C with PTFE Propeller shaft splines 92-802859A 1

NOTE: Propellers used on the 31.75 mm (1‑1/4 in.) diameter propeller shaft
require the heavy‑duty propeller hub kit.

5.

Heavy‑duty propeller hub—Install the propeller hub, propeller, washer,
Belleville washer, washer, and propeller nut onto the shaft.

a - Propeller nut
b - Washer
c - Belleville washer
d - Washer
e - Propeller
f - Propeller hub

6. Place a block of wood between the gearcase and the propeller. Tighten
the propeller nut to the specified torque.

2691

Description

Nm lb‑in. lb‑ft

Propeller nut 75 – 55.3

Spark Plug Inspection and Replacement

1.

Remove the top cowl. Refer to Top Cowl Removal and Installation.

a

b

c

d

e

f

44856

MAINTENANCE

eng 61

2. Grasp the spark plug boot and use a twisting motion to assist removing
the spark plug boot from the spark plugs.

63312

Spark plug boot

3. Remove the spark plug with a 14 mm deep socket.

NOTE: Replace the spark plug if the electrode is worn; the insulator is rough,
cracked, broken, or blistered; or if the precious metal is not visible on the spark
plug electrode.

IMPORTANT: The color of the plug may not accurately reflect its condition. To
accurately diagnose a faulty plug, inspect the precious metal on the plug's
electrode. If no precious metal is visible, replace the plug.

a - Precious metal

a

9381

MAINTENANCE

62 eng

4.

Check the spark plug gap. Refer to General Information ‑ Specification.

27848

a. All of the spark plugs should have the gap checked and corrected as

necessary before installation.

b. Measure the gap with a feeler gauge or pin gauge. Never use a

wedge‑type gap checking tool to inspect or to adjust the gap.

c. If an adjustment is necessary, do not pry or apply any force on the

center electrode. This is critical with any type of spark plug that has a
wear surface, such as platinum or iridium added to either the ground
electrode or the center electrode.

d. When it is necessary to widen the gap, use a tool that only pulls back

on the ground electrode without touching the center electrode, the
porcelain, or the wear portion of the ground electrode.

e. When it is necessary to close the gap, gently tap the plug ground

electrode on a hard surface.

5. Saltwater use—Apply Anti‑Seize Compound only onto the threads of the
spark plugs.

Tube Ref

No.

Description Where Used Part No.

81

Anti-Seize
Compound

Spark plug threads 92-898101389

6. Before installing the spark plugs, remove any dirt on the spark plug seat
area. Install the plugs finger‑tight and then tighten an additional 1/4 turn or
tighten to the specified torque.

Description

Nm lb‑in. lb‑ft

Spark plug 20 177 –

7. Insert the spark plug boot into the valve cover. The boot is self‑aligning
with the spark plug.

MAINTENANCE

eng 63

8. Push on the end of the spark plug boot to ensure the boot is completely
engaged and seated onto the spark plug.

63315

Push the spark plug boot

9. Install the top cowl.

Fuses

IMPORTANT: An ATC fuse has the fuse element enclosed or sealed inside the
plastic housing. This type of fuse must be used for marine applications. Marine
applications are exposed to environments that may have the potential to
accumulate explosive vapors. ATO fuses have exposed elements and should
never be used in marine applications.

The electrical wiring circuits on the outboard are protected from overload with
fuses. If a fuse is open, try to locate and correct the cause of the overload. If
the cause is not found, the fuse may open again.

MAINTENANCE

64 eng

1. Locate the fuse holder on the port side of the engine and remove the
cover from the fuse holder.

63317

2. Remove the suspected open fuse and look at the silver band inside the
fuse. If the band is broken (open), replace the fuse.

MAINTENANCE

eng 65

IMPORTANT: Replace the fuse with a new fuse with the same amp rating.

a - Ignition coils ‑ 20 amp
b - Oxygen sensor ‑ 10 amp
c - Fuel pumps ‑ 20 amp
d - Diagnostics ‑ 2 amp
e - Fuel injectors ‑ 20 amp
f - Advanced sound control driver ‑ 5 amp
g - Power driver ‑ 20 amp
h - Spare fuses (3)
i - Good fuse
j - Open fuse

Alternator Drive Belt

The alternator drive belt is located under the flywheel shroud–intake air
induction plenum. The alternator drive belt inspection must be completed by an
authorized Mercury dealer at the recommended interval. Refer to Inspection
and Maintenance Schedule.

Lubrication Points

1. Lubricate the following with Extreme Grease or 2‑4‑C with PTFE.

Tube Ref

No.

Description Where Used Part No.

Extreme Grease Swivel bracket, tilt lock, propeller shaft 8M0071842

63805

j

5

20

2

10

20

20

20

abcde

f

g

SPARE FUSES

h

i

MAINTENANCE

66 eng

Tube Ref

No.

Description Where Used Part No.

95

2-4-C with PTFE

Swivel bracket, tilt lock, tilt tube,

propeller shaft

92-802859A 1

• Lubricate the tilt lock through the grease fitting.

• Lubricate the swivel bracket through the grease fitting.

a - Tilt lock grease fitting
b - Swivel bracket grease fitting

• Lubricate the tilt tube through the grease fitting.

66321

Tilt tube grease fitting

66320

a

b

MAINTENANCE

eng 67

•

Propeller shaft—Refer to Propeller Replacement for removal and
installation of the propeller. Apply a generous amount of lubricant to
the entire propeller shaft to prevent the propeller hub from seizing to
the shaft.

66448

2. Lubricate the steering linkage with oil.

63797

Lubricate with oil

Trim Thrust Guide Wear Pad

This power package utilizes trim thrust guides which are part of the transom
clamp casting and swivel bracket. The thrust guide improves the stability of the
power package at high speeds when the engine is trimmed out. When the
engine is trimmed up or down, the swivel bracket thrust guide will rub against
the thrust guide wear pads which are mounted on the transom clamps. Replace
the thrust guide wear pads if the heads of the mounting screws are becoming
flush with the wear pad surface. Failure to replace the thrust guide wear pad
before the mounting screws are flush with the pad, may cause damage to the
swivel bracket. Damage to the swivel bracket caused by the thrust guide wear
pad mounting hardware is not covered under warranty. Refer to the Inspection
and Maintenance Schedule for the proper maintenance interval.

MAINTENANCE

68 eng

IMPORTANT: When replacing the thrust guide wear pads, replace both pads
and install new retaining hardware.

66265

Checking Power Trim Fluid (Single‑Ram Trim)

1. Trim the outboard in the full down/in position.

2. Check the fluid level in the trim pump reservoir. The level should be
between the minimum ("MIN") and the maximum ("MAX") level on the
reservoir.

3. If necessary, remove the yellow fill cap and add Power Trim and Steering
Fluid until the level in the reservoir reaches the minimum level. It is
acceptable to fill the reservoir beyond the minimum level, but do not
overfill past the maximum level.

114

15033

MAINTENANCE

eng 69

Tube Ref

No.

Description Where Used Part No.

114

Power Trim and
Steering Fluid

Trim pump reservoir 92-858074K01

4. Trim the outboard full up and down to purge air out of the system. The
fluid level may drop. Add Power Trim and Steering Fluid if necessary, but
do not overfill past the maximum level.

5. Replace the fill cap.

Checking Hydraulic Steering Fluid

!

WARNING

Dirt or contaminants in the hydraulic steering system can damage the
steering system's internal components. Damaged components can lead to
serious injury or death due to loss of boat control. Do not allow dirt or
contamination to enter the helm, lines, or cylinder of this steering system and
perform all hydraulic inspections, service, or assembly procedures in a clean
work area.

IMPORTANT: Check the hydraulic steering fluid level on a regular basis. The
steering system must be full of fluid to ensure the steering helm will not
introduce air into the steering system. A hydraulic steering system which has
entrained air will have spongy or unresponsive steering control which could
compromise the operator's ability to control the boat. On dual helm steering
systems, always check the upper steering helm first. If the system must be
purged of entrained air, one person may not be able to completely fill and purge
the air from the steering system. See your dealer if you have questions on your
steering system or refer to the installation instructions included with your
steering system.

Checking Power Steering Fluid

!

WARNING

Dirt or contaminants in the hydraulic steering system can damage the
steering system's internal components. Damaged components can lead to
serious injury or death due to loss of boat control. Do not allow dirt or
contamination to enter the helm, lines, or cylinder of this steering system and
perform all hydraulic inspections, service, or assembly procedures in a clean
work area.

MAINTENANCE

70 eng

Remove the power steering cover and fill cap to check the fluid level. The fluid
level should be slightly below the bottom of the fill hole. Use Synthetic Power
Steering Fluid SAE 0W‑30, if needed.

a - Power steering cover
b - Fill cap
c - Fill/full level

Tube Ref

No.

Description Where Used Part No.

138

Synthetic Power
Steering Fluid SAE
0W-30

Power steering system 92-858077K01

Changing Engine Oil and Filter

ENGINE OIL CAPACITY

Engine oil capacity is approximately 6.6 Liter (7.0 US qt).
IMPORTANT: Tilt the outboard out/up past vertical for approximately one

minute to allow any trapped oil to drain back to the oil sump.

OIL CHANGE ON LAND PROCEDURE

1. Tilt the outboard out/up past vertical for approximately one minute to allow
any trapped oil to drain back to the oil sump.

2. Tilt the outboard to a vertical position.

3. Use a 16 mm (5/8 in.) wrench and loosen the oil drain valve so that it can
be turned by hand. Be careful not to open the valve too far allowing oil to
drain.

4. Attach a 12 mm (7/16 in.) inside diameter drain hose to the oil drain valve.
Position the opposite end of the hose into an appropriate container. The
container should be large enough to hold more than 9.8 Liter (10 US qt).

5. Loosen the oil drain valve 2‑1/2 turns to allow oil to drain. Do not exceed
2‑1/2 turns.

29315

MAINTENANCE

eng 71

IMPORTANT: Do not loosen the oil drain valve more than 2‑1/2 turns out. The
oil seal could get damaged beyond 2‑1/2 turns.

a - Oil drain valve
b - Drain hose
c - Loosen 2‑1/2 turns maximum

6. After the oil has drained, hand‑tighten the oil drain valve (clockwise) and
remove the oil drain hose.

7. Tighten the oil drain valve to the specified torque. Clean up any oil in the
valve area.

Description

Nm lb‑in. lb‑ft

Oil drain valve 15 132.7 –

IMPORTANT: Overtightening the oil drain valve can damage the oil sump.

8. Add the appropriate amount of engine oil.

OIL CHANGE ON WATER PROCEDURE

1. Tilt the outboard out/up past vertical for approximately one minute to allow
any trapped oil to drain back to the oil sump.

2. Tilt the outboard to a vertical position.

b

a

1

2

2-

c

63398

MAINTENANCE

72 eng

3. Push down on the port side of the service access door to unlock and open
the door.

64230

Push here to unlock

4. Remove the dipstick.

5. Install the oil drain hose onto the crankcase oil pump. Verify the hose is
securely attached.

a - Crankcase oil pump
b - Oil drain hose

a

b

63845

MAINTENANCE

eng 73

Crankcase Oil Pump 802889A1

11591

Aids in the removal of engine oil without
draining the crankcase.

Oil Drain Hose 8M0137866

64627

Aids in the removal of engine oil without
draining the crankcase. Connect to the
crankcase oil pump.

6. Install the crankcase oil pump assembly onto the dipstick tube. Verify the
pump is securely attached to the tube by pulling it up lightly.

a - Oil drain hose
b - Lock button

7. Place the drain tube of the crankcase oil pump into an appropriate
container. The container should be large enough to hold more than

9.8 Liter (10 US qt).

8. Extract the engine oil with the pump.

9. Allow the drain tube to completely drain before removing the oil pump
from the dipstick tube.

10. Press on the oil drain hose lock button to release it from the dipstick tube.

a

b

63843

MAINTENANCE

74 eng

11. Install the dipstick. Verify it is completely inserted.

12. Add the appropriate amount of engine oil.

CHANGING OIL FILTER

1. Remove the plug from the oil trough and attach a 12 mm (7/16 in.) I.D.
drain hose to the fitting. Place the opposite end of the hose into an
appropriate container.

2. Remove the old filter by turning the filter counterclockwise.

a - Oil filter
b - Drain hose

3. Allow the oil in the trough to drain.

4. Clean the remaining oil from the oil trough and filter mounting base area.

5. Remove the hose and install the plug.

6. Apply a film of clean oil to the filter gasket. Do not use grease. Install the
new filter until the gasket contacts the base and then tighten 3/4 to 1 turn.

OIL FILLING

Remove the oil fill cap and add approximately 6.6 Liter (7.0 US qt) of the
recommended oil. This will bring the oil level within the operating range.

a - Oil fill cap
b - Dipstick

a

b

63399

a

b

63401

MAINTENANCE

eng 75

NOTE: It is not necessary to check the oil level immediately after changing the
oil. The engine must be run for a while and then turned off for one hour or
longer before checking the oil level. Refer to

Checking Engine Oil Level.

Checking Engine Oil Level

After the engine oil has been changed, the engine should be run for a few
minutes and then turned off, allowing one hour or longer before checking the oil
level.

IMPORTANT: For an accurate oil level reading, the engine must be vertical for
several minutes before removing the dipstick.

1. Remove the dipstick and observe the area of the five beads.

2. The bead or crosshatch which shows oil furthest from the end is the oil
level.

63468

Oil level example

DIPSTICK BEAD OIL LEVEL OVERVIEW

New oil (level) may be difficult to identify which is why the crosshatch between
the beads are part of the dipstick assembly. When checking the oil level, if oil is
on any of the five oil range beads or four crosshatch, the oil level is within the
safe operating range. When the oil level is only on the lowest oil range bead,
the operator can add 1.8 Liter (2 US qt) of oil and the level will remain within
the safe operating range. When the oil becomes dark from hours of product
use, it will be easier to identify the oil level on the dipstick.

IMPORTANT: Repeated removal and insertion of the dipstick to check the oil
level will subsequently deposit oil further up the dipstick tube which potentially
may cause an error reading the oil level.

a - Safe operating range
b - General area after an oil change
c - Add 1.8 Liter (2 US qt) of oil

c

a

b

65510

MAINTENANCE

76 eng

Exhaust Water Strainer Inspection

IMPORTANT: The water strainer is an integral component of the cooling
system. It should be inspected every 100 hours of operation or once a year,
whichever occurs first.

1.

Remove the top cowl. Refer to Top Cowl Removal and Installation.

2. Remove the hose from the exhaust water spray inlet assembly. Press on
the hose lock and pull the hose off the assembly.

a - Exhaust water spray inlet assembly
b - Hose lock

3. Remove the strainer from the assembly.

64630

Strainer

a

b

64629

MAINTENANCE

eng 77

4. Inspect the strainer for debris, blockage, or accumulation of mineral
deposits. Flush the strainer with fresh water. Use a nylon bristle brush to
help remove debris, blockage, or mineral deposits. If the strainer cannot
be cleared of debris, blockage, mineral deposits, or if the strainer is
damaged, replace the strainer.

64631

5. Install the strainer into the exhaust water spray inlet assembly.

6. Install the hose onto the assembly. Verify the hose is secure by pulling up
on the hose.

Gearcase Lubricant

GEARCASE LUBRICATION

When adding or changing gearcase lubricant, visually check for the presence of
water in the lubricant. If water is present, it may have settled to the bottom and
will drain out prior to the lubricant, or it may be mixed with the lubricant, giving it
a milky colored appearance. If water is noticed, have the gearcase checked by
your dealer. Water in the lubricant may result in premature bearing failure or, in
freezing temperatures, will turn to ice and damage the gearcase.

Examine the drained gearcase lubricant for metal particles. A small amount of
metal particles indicates normal gear wear. An excessive amount of metal
filings or larger particles (chips) may indicate abnormal gear wear and should
be checked by an authorized dealer.

300R HD REQUIRED GEARCASE LUBRICATION

Extreme Performance Gear Lube ‑ SAE 90

GEARCASE LUBRICANT CAPACITY

NOTE: Gearcase lubricant capacity is approximate.

Gearcase Lubricant Capacity

Sport Master

Right‑hand rotation

620 mL (21.0 fl oz)

Left‑hand rotation

137 mm (5.44 in.)

Right‑hand rotation 720 mL (24.4 fl oz)

Left‑hand rotation 680 mL (23.0 fl oz)

DRAINING AND FILLING THE GEARCASE

Draining Gearcase

1. Place the outboard in a vertical operating position.

2.

Remove the propeller. Refer to Propeller Replacement.

3. Place a pan below the gear housing to capture the lubricant.

MAINTENANCE

78 eng

4. Remove the lubricant level plug and fill/drain plug. Allow a sufficient
amount of time for the gearcase to drain. Depending on the ambient air
temperature, it may take 30 minutes for the gearcase to completely drain.

a - Lubricant level plug
b - Fill/drain plug

Filling the Gearcase

1. After the gearcase has been drained, fill the gearcase through the fill/drain
hole.

2. Add the specified gear lubricant.

IMPORTANT: Replace the sealing washers if damaged.

3. Allow a few minutes for the lubricant level to stabilize in the gearcase
before installing the lubricant level plug. Install the lubricant level plug.

4. Remove the tube and install the fill/drain plug.

5. Tighten the plugs to the specified torque.

Description

Nm lb‑in. lb‑ft

Plugs 11.3 100 –

Checking Lubricant Level

1. Place the outboard in a vertical operating position. Allow up to 30 minutes
for the lubricant level to stabilize in the gear housing.

2. Remove the lubricant level plug. Verify the sealing washer is not adhered
to the bearing carrier. The lubricant should be level with the hole or slowly
leak from the hole.

IMPORTANT: Replace the sealing washers if damaged.

3. If lubricant is not visible at the lubricant level hole, remove the fill/drain
plug and add lubricant until it appears at the lubricant level hole.

4. Stop adding lubricant.

a

b

66264

MAINTENANCE

eng 79

5. Remove the lubricant tube and install the fill/drain plug and sealing
washer.

6. Tighten the plugs to the specified torque.

Description Nm lb‑in. lb‑ft
Plugs 11.3 100 –

MAINTENANCE

80 eng

Storage Preparation

The major consideration in preparing your outboard for storage is to protect it
from rust, corrosion, and damage caused by freezing of trapped water.

The following storage procedures should be followed to prepare your outboard
for out of season storage or prolonged storage (two months or longer).

NOTICE

Without sufficient cooling water, the engine, the water pump, and other
components will overheat and suffer damage. Provide a sufficient supply of
water to the water inlets during operation.

FUEL SYSTEM

IMPORTANT: Gasoline containing alcohol (ethanol or methanol) can cause a
formation of acid during storage and can damage the fuel system. If the
gasoline being used contains alcohol, it is advisable to drain as much of the
remaining gasoline as possible from the fuel tank, remote fuel line, and engine
fuel system.

IMPORTANT: This outboard is equipped with a closed fuel system when the
engine is not running. With this closed system, fuel within the engine's fuel
system, other than the fuel tank, will remain stable during normal storage
periods without the addition of fuel treatment stabilizers.

Fill the fuel tank and engine fuel system with treated (stabilized) fuel to help
prevent formation of varnish and gum. Proceed with the following instructions.

• Portable fuel tank ‑ Pour the required amount of Quickstor Fuel Stabilizer
(follow instructions on container) into fuel tank. Tip fuel tank back and
forth to mix stabilizer with the fuel.

• Permanently installed fuel tank ‑ Pour the required amount of Quickstor
Fuel Stabilizer (follow instructions on container) into a separate container
and mix with approximately one liter (one quart) of gasoline. Pour this
mixture into fuel tank.

Tube Ref

No.

Description Where Used Part No.

124

Quickstor Fuel
Stabilizer

Fuel tank 92-8M0047932

Protecting External Outboard Components

• Touch up any paint nicks. See your dealer for touch‑up paint.

• Spray Quicksilver or Mercury Precision Lubricants Corrosion Guard on
external metal surfaces (except corrosion control anodes).

Tube Ref

No.

Description Where Used Part No.

120

Corrosion Guard External metal surfaces 92-802878 55

STORAGE

eng 81

Protecting Internal Engine Components

IMPORTANT: Refer to Maintenance ‑ Spark Plug Inspection and Replacement
for correct procedure for removing spark plugs.

• Remove the high tension spark plug leads and spark plugs.

• Spray approximately 30 ml (1 fl oz) of Storage Seal Rust Inhibitor into
each spark plug hole.

Tube Ref

No.

Description Where Used Part No.

119

Storage Seal Rust
Inhibitor

Spark plug holes 92-858081K03

• Actuate key/push button start switch to crank the engine through one start
cycle, which will distribute the storage seal throughout the cylinders.

• Install spark plugs and the high tension spark plug leads.

Gearcase

•

Drain and refill the gearcase lubricant. Refer to Gearcase Lubrication.

Positioning Outboard for Storage

Store outboard in an upright (vertical) position to allow water to drain out of the
outboard.

NOTICE

Storing the outboard in a tilted position can damage the outboard. Water
trapped in the cooling passages or rain water collected in the propeller
exhaust outlet in the gearcase can freeze. Store the outboard in the full down
position.

Battery Storage

• Follow the battery manufacturer's instructions for storage and charging.

• Remove the battery from the boat and check water level. Charge if
necessary.

• Store the battery in a cool, dry place.

• Periodically check the water level and charge the battery during storage.

STORAGE

82 eng

Starter Motor Will Not Crank the Engine

POSSIBLE CAUSES

• Lanyard stop switch not in RUN position.

•

Open 20‑amp fuse. Check the power driver fuse. Refer to Maintenance
section.

• Outboard is not shifted to neutral position.

• Weak battery or battery connections are loose or corroded.

• Ignition key switch failure.

• Wiring or electrical connection faulty.

• Starter motor solenoid or starter relay failure.

Engine Will Not Start

POSSIBLE CAUSES

•

Incorrect starting procedure. Refer to Operation section.

• Old or contaminated gasoline.

• Fuel is not reaching the engine.

• Fuel tank is empty.

• Fuel tank vent not open or restricted.

• Fuel line is disconnected or kinked.

•

Fuel filter is obstructed. Refer to Maintenance section.

• Fuel pump failure.

• Fuel tank filter obstructed.

• Ignition system component failure.

•

Spark plugs fouled or defective. Refer to Maintenance section.

Engine Runs Erratically

POSSIBLE CAUSES

• Overheating ‑ Warning horn not working.

• Low oil pressure. Check oil level.

•

Spark plugs fouled or defective. Refer to Maintenance section.

• Incorrect setup and adjustments.

• Fuel is being restricted to the engine.
a.

Engine fuel filter is obstructed. Refer to Maintenance section.
b. Fuel tank filter obstructed.
c. Stuck antisiphon valve located on permanently built‑in type fuel tanks.
d. Fuel line is kinked or pinched.

• Fuel pump failure.

TROUBLESHOOTING

eng 83

• Ignition system component failure.

Performance Loss

POSSIBLE CAUSES

• Overheating ‑ Warning horn not working.

• Low oil pressure. Check oil level.

• Throttle not opening fully.

• Damaged propeller or improper propeller size.

• Incorrect engine timing, adjustment, or setup.

• Boat overloaded or load improperly distributed.

• Excessive water in bilge.

• Boat bottom is dirty or damaged.

Battery Will Not Hold Charge

POSSIBLE CAUSES

• Battery connections are loose or corroded.

• Low electrolyte level in battery.

• Worn out or inefficient battery.

• Excessive use of electrical accessories.

• Defective rectifier, alternator, or voltage regulator.

• Open circuit in the alternator output wire (fused link).

TROUBLESHOOTING

84 eng

Service Assistance

LOCAL REPAIR SERVICE

If you need service for your Mercury‑outboard‑powered boat, take it to your
authorized dealer. Only authorized dealers specialize in Mercury products and
have factory‑trained mechanics, special tools and equipment, and genuine
Quicksilver parts and accessories to properly service your engine.

NOTE: Quicksilver parts and accessories are engineered and built by Mercury
Marine specifically for your power package.

SERVICE AWAY FROM HOME

If you are away from your local dealer and the need arises for service, contact
the nearest authorized dealer. If, for any reason, you cannot obtain service,
contact the nearest Regional Service Center. Outside the United States and
Canada, contact the nearest Marine Power International Service Center.

STOLEN POWER PACKAGE

If your power package is stolen, immediately advise the local authorities and
Mercury Marine of the model and serial numbers and to whom the recovery is
to be reported. This information is maintained in a database at Mercury Marine
to aid authorities and dealers in the recovery of stolen power packages.

ATTENTION REQUIRED AFTER SUBMERSION

1. Before recovery, contact an authorized Mercury dealer.

2. After recovery, immediate service by an authorized Mercury dealer is
required to reduce the possibility of serious engine damage.

REPLACEMENT SERVICE PARTS

!

WARNING

Avoid fire or explosion hazard. Electrical, ignition, and fuel system
components on Mercury Marine products comply with federal and
international standards to minimize risk of fire or explosion. Do not use
replacement electrical or fuel system components that do not comply with
these standards. When servicing the electrical and fuel systems, properly
install and tighten all components.

Marine engines are expected to operate at or near full throttle for most of their
lives. They are also expected to operate in both fresh and saltwater
environments. These conditions require numerous special parts.

PARTS AND ACCESSORIES INQUIRIES

Direct any inquiries concerning genuine Mercury Precision Parts® or
Quicksilver Marine Parts and Accessories® to a local authorized dealer.
Dealers have the proper systems to order parts and accessories, if they are not
in stock. Engine model and serial number are required to order correct parts.

OWNER SERVICE ASSISTANCE

eng 85

RESOLVING A PROBLEM

Satisfaction with your Mercury product is important to your dealer and to us. If
you ever have a problem, question or concern about your power package,
contact your dealer or any authorized Mercury dealership. If you need
additional assistance:

1. Talk with the dealership's sales manager or service manager.

2. If your question, concern, or problem cannot be resolved by your
dealership, please contact the Mercury Marine Service Office for
assistance. Mercury Marine will work with you and your dealership to
resolve all problems.

The following information will be needed by the Customer Service:

• Your name and address

• Your daytime telephone number

• The model and serial numbers of your power package

• The name and address of your dealership

• The nature of the problem

CONTACT INFORMATION FOR MERCURY MARINE CUSTOMER
SERVICE

For assistance, call, fax, or write to the geographic office in your area. Please
include your daytime telephone number with mail and fax correspondence.

United States, Canada

Telephone

English [phone]
Français [phone]

Mercury Marine
W6250 Pioneer Road
P.O. Box 1939
Fond du Lac, WI 54936-1939

Fax

English [phone]
Français [phone]

Website www.mercurymarine.com

Australia, Pacific
Telephone [phone] Brunswick Asia Pacific Group

41–71 Bessemer Drive
Dandenong South, Victoria 3175
Australia

Fax [phone]

Europe, Middle East, Africa
Telephone [phone] Brunswick Marine Europe

Parc Industriel de Petit-Rechain
B-4800 Verviers,
Belgium

Fax [phone]

OWNER SERVICE ASSISTANCE

86 eng

Mexico, Central America, South America, Caribbean
Telephone [phone] Mercury Marine

11650 Interchange Circle North
Miramar, FL 33025
U.S.A.

Fax [phone]

Japan
Telephone [phone] Kisaka Co., Ltd.

4‑130 Kannabecho, Sakai‑ku
Sakai‑shi, Osaka 590‑0984, Japan

Fax [phone]

Asia, Singapore
Telephone [phone] Brunswick Asia Pacific Group

T/A Mercury Marine Singapore Pte Ltd
29 Loyang Drive
Singapore, 508944

Fax [phone]

Ordering Literature

Before ordering literature, have the following information about your power
package available:

Model

Serial Number

Horsepower Year

UNITED STATES AND CANADA

For additional literature for your Mercury Marine power package, contact your
nearest Mercury Marine dealer or contact:

Mercury Marine

Telephone Fax Mail

(920) 929‑5110

(USA only)

(920) 929‑4894

(USA only)

Mercury Marine

Attn: Publications Department

P.O. Box 1939

Fond du Lac, WI 54936-1939

OUTSIDE THE UNITED STATES AND CANADA

Contact your nearest Mercury Marine authorized service center to order
additional literature that is available for your particular power package.

OWNER SERVICE ASSISTANCE

eng 87

Submit the following
order form with payment
to:

Mercury Marine
Attn: Publications Department
W6250 Pioneer Road
P.O. Box 1939
Fond du Lac, WI 54936-1939

Ship To: (Copy this form and print or type–This is your shipping label)

Name

Address

City, State, Province

ZIP or postal code

Country

Quantity Item Stock Number Price Total

. .
. .
. .
. .
. .

Total Due .

OWNER SERVICE ASSISTANCE

88 eng

Maintenance Log

Record all maintenance performed on your outboard here. Be sure to save all
work orders and receipts.

Date Maintenance Performed Engine Hours

MAINTENANCE LOG

eng 89