Mercury MerCruiser 8.1S Installation Manual

The following are registered trademarks of
Brunswick Corporation: Merc, MerCathode,
MerCruiser, Mercury, Mercury Marine,
Quicksilver, RideGuide and MMPP.

GASOLINE ENGINE 8.1S INBOARD MODELS
INSTALLATION MANUAL

NOTICE to INSTALLER

After Completing Installation, These Instructions Should Be Placed With The Product For The
Owner’s Future Use.

NOTICE to COMMISSIONING DEALER

Predelivery Preparation Instructions Must Be Performed Before Delivering Boat To The Product
Owner.

Table of Contents

General Information 2. . . . . . . . . . . . . . . . . . . .

Notice to Installer 2. . . . . . . . . . . . . . . . . . . . .

Quicksilver Products 3. . . . . . . . . . . . . . . . . .

Lubricants / Sealants / Adhesives 3. . . . . . .

Torque Specifications 3. . . . . . . . . . . . . . . . .

Serial Number Decal Placement 4. . . . . . . .

Engine Rotation 4. . . . . . . . . . . . . . . . . . . . . .

Transmissions 4. . . . . . . . . . . . . . . . . . . . . . . . .

Velvet Drive Transmissions 4. . . . . . . . . . . .

ZF / Hurth Transmissions 5. . . . . . . . . . . . . .

Propeller Rotation 6. . . . . . . . . . . . . . . . . . . .

Installation Requirements 9. . . . . . . . . . . . . .

Engine Bed 9. . . . . . . . . . . . . . . . . . . . . . . . . .

Engine Compartment 9. . . . . . . . . . . . . . . . .

Exhaust System 12. . . . . . . . . . . . . . . . . . . . . .

Fuel Delivery System 16. . . . . . . . . . . . . . . . .

Battery 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

EFI Electrical System Precautions 20. . . . . .

Instrumentation 20. . . . . . . . . . . . . . . . . . . . . . .

Propeller Selection 21. . . . . . . . . . . . . . . . . . . .

Throttle/Shift Remote Control and Cables 22

Seawater Connections 22. . . . . . . . . . . . . . . .

Hot Water Heater 23. . . . . . . . . . . . . . . . . . . . .

Engine Installation 24. . . . . . . . . . . . . . . . . . . . .

Engine Oil Dipstick Location 24. . . . . . . . . . .

Battery Cable Connection 24. . . . . . . . . . . . . .

Engine Mount Pre-Adjustment 25. . . . . . . . . .

Initial Engine Alignment 26. . . . . . . . . . . . . . .

Final Engine Alignment 29. . . . . . . . . . . . . . . .

Engine Connections 34. . . . . . . . . . . . . . . . . . . .

Seawater Pickup Pump Connection 34. . . . .

Fuel Supply Connection 34. . . . . . . . . . . . . . .

Audio Warning System Connection 35. . . . .

Electrical Connections 36. . . . . . . . . . . . . . . . .

Exhaust System 37. . . . . . . . . . . . . . . . . . . . . .

Shaft Log Seal Connection 38. . . . . . . . . . . . .

Shift Cable Installation And Adjustment 39.

Velvet Drive Transmissions

- 5000 Series 39. . . . . . . . . . . . . . . . . . . . . . .

Velvet Drive Transmissions - 72C In-Line 43

Hurth Transmissions 47. . . . . . . . . . . . . . . . . .

Predelivery Preparation 52. . . . . . . . . . . . . . . . .

Battery Connection 52. . . . . . . . . . . . . . . . . . .

Test Running Engine 52. . . . . . . . . . . . . . . . . .

Boat In The Water Tests 52. . . . . . . . . . . . . . .

Cold Weather and

Extended Storage Draining 53. . . . . . . . . . . .

Coolant And Water Flow Diagrams 56. . . . . .

Predelivery Inspection 58. . . . . . . . . . . . . . . . . .

90-863080002 JANUARY 2001 Printed in U.S.A. -  2001, Mercury Marine Page 1 of 58

GASOLINE ENGINE 8.1 S INBOARD MODELS

General Information

Notice to Installer

Throughout this publication, Warnings and Cautions (accompanied by the International
Hazard Symbol

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
to these special instructions when performing the service, plus common sense operation,
are major accident prevention measures.

Hazards or unsafe practices which COULD result in severe personal injury or death.

Hazards or unsafe practices which could result in minor personal injury or product
or property damage.

IMPORTANT: Indicates information or instructions that are necessary for proper in­stallation and/or operation.

!

) are used to alert the installer to special instructions concerning a

WARNING

CAUTION

This installation manual has been written and published by Mercury Marine to aid the boat
manufacturer involved in the application and installation of the products described herein.

It is assumed that these personnel are familiar with the installation procedures of these
products, or like or similar products manufactured and marketed by Mercury Marine. That
they have been trained in the recommended installation procedures of these products which
includes the use of mechanics’ common hand tools and the special Mercury Marine or
recommended tools from other suppliers.

It is the responsibility of the OEM to select the appropriate engine/transom/drive package
(including the correct gear ratio and propeller) for a given boat. Making an appropriate
selection requires knowledge of the boat (weight, length, hull design, intended use and duty
cycle, desired speed) that is uniquely in the possession of the OEM. While Mercury employs
people capable of assisting the OEM on such issues, the final decision rests with the OEM.
Mercury recommends that any new or unique hull/power package combination be
thoroughly water tested prior to sale, to verify (among other things) that the boat performs
as desired, and that the engine runs in the appropriate rpm range.

We could not possibly know of and advise the marine trade of all conceivable procedures
by which an installation might be performed, and of the possible hazards and/or results of
each method. We have not undertaken any such wide evaluation. Therefore, anyone who
uses an installation procedure and/or tool, which is not recommended by the manufacturer,
first must completely satisfy himself that neither his nor the product’s safety will be
endangered by the installation procedure selected.

It is recommended that a Mercury Marine Sales Application Engineer (SAE) be contacted
for assistance if specific application or installation problems are encountered.

All information, illustrations, and specifications contained in this manual are based on the
latest product information available at time of publication. As required, revisions to this
manual will be sent to all OEM boat companies.

Page 2 of 58

Quicksilver Products

Quicksilver gauges, remote controls, steering systems, propeller shaft couplers, and other
accessories are available for this product. Refer to Mercury Precision Parts/Quicksilver
Accessories Guide for complete listing.

This Guide is available from:

Outside of U.S.A., order through Distribution Center, or Distributor.

Lubricants / Sealants / Adhesives

2-4-C Marine Lubricant with Teflon 92-825407A3
Liquid Neoprene 92-25711--3
Perfect Seal 92-34227--1

GASOLINE ENGINE 8.1 S INBOARD MODELS

Attn: Parts Department

Mercury Marine

W6250 W. Pioneer Road

P.O. Box 1939

Fond du Lac, WI 54936-1939

Description Part Number

Torque Specifications

Engine Mount Bracket Screws 47 64
Trunnion Clamping Bolt and Nut 50 68
Propeller Shaft Nut 50 68
Exhaust Manifold Screw 20 27
Fuel Line Fitting See Note.
Coupler Bolts 50 68

Note: Refer to Fuel Delivery System - Special Information For All Gasoline Engines.

Description lb-in. lb-ft Nm

Page 3 of 58

GASOLINE ENGINE 8.1 S INBOARD MODELS

Serial Number Decal Placement

There are three engine serial number decal strips provided with each power package. One
should be used for each of the following:

• Engine Specification Decal

• Warranty Registration Card

• Operation and Maintenance Manual identification page.

Affix engine serial number decal to specification / serial number decal in position shown.

a-Specification/Serial Number Decal

Engine Rotation

Engine rotation is described when observed from the rear of the engine (transmission end)
looking forward (water pump end).

Engine rotation is indicated on engine specifications and serial number decal.

Transmissions

Velvet Drive Transmissions

On the Velvet Drive 5000A and 5000V Transmissions the transmission identification plate
indicates gear ratio, serial number and model.

a

77643

a

Velvet Drive 5000A - 8° Down-Angle T ransmission Shown (5000V V-Drive Similar)

a-Transmission Identification Plate

Page 4 of 58

71778

On Velvet Drive 72C Transmissions the gear ratio (in forward gear) is marked on
transmission identification plate. Transmission output shaft rotation and propeller rotation
required (in forward gear) is indicated on a decal on transmission case. Transmission
rotation is described when viewed from the rear of transmission.

Typical Transmission Shown

a-Transmission Identification Plate
b-Output Flange Rotation Decal

ZF / Hurth Transmissions

GASOLINE ENGINE 8.1 S INBOARD MODELS

b

a

22556

On the Hurth 8° Down-Angle and V-Drive Transmissions the transmission identification
plate indicates gear ratio, serial number and model.

a

73587

Typical Hurth Down-Angle Transmission Shown (V-Drive Identification Plate
Similarly Located)

a-Transmission Identification Plate

Page 5 of 58

GASOLINE ENGINE 8.1 S INBOARD MODELS

Propeller Rotation

Propeller rotation is not necessarily the same as engine rotation. Refer to the appropriate
following information and drawings for specific information.

These transmissions are full power reversing transmissions, allowing a standard, LH
rotation engine to be used for both propeller rotations. Propeller rotation (output shaft
rotation) is determined by shift cable attachment at the remote control. Be sure to use
correct rotation propeller and shift cable hook up for direction desired.

a

c

b

Velvet Drive 5000A - 8° Down-Angle Transmission

b

a

b

f

g

d

e

71888

d

b

74604

Velvet Drive 5000V - V-Drive Transmissions

a-Direction Of Shift Lever Engagement (Toward Flywheel)
b-Engine/Transmission Input Shaft Rotation Direction (LH)
c-Transmission Output/Propeller Shaft Rotation Direction (LH)
d-Direction Of Shift Lever Engagement (Away From Flywheel)
e-Transmission Output/Propeller Shaft Rotation Direction (RH)

f-Transmission Output/Propeller Shaft Rotation Direction (LH As Viewed At

Propeller)

g-Transmission Output/Propeller Shaft Rotation Direction (RH As Viewed At The

Propeller)

Page 6 of 58

Propeller Rotation (Continued)

GASOLINE ENGINE 8.1 S INBOARD MODELS

a

b

c

e

ZF / Hurth 630A or 800A - 8° Down-Angle Transmissions

a

b

c

72959

d

e

d

b

25506

b

72959

ZF / Hurth 630V - V-Drive Transmissions

a-Direction Of Shift Lever Engagement (Toward Flywheel)
b-Engine/Transmission Input Shaft Rotation Direction (LH)
c-Transmission Output/Propeller Shaft Rotation Direction (LH)
d-Direction Of Shift Lever Engagement (Away From Flywheel)
e-Transmission Output/Propeller Shaft Rotation Direction (RH)

PROPELLER ROTATION ON DUAL INSTALLATIONS

Best all-around performance usually is obtained by installing engines so that propellers turn
outboard (looking at the stern).

b

Outboard Propeller Rotation

a-RH Rotation
b-LH Rotation

a

22457

Page 7 of 58

GASOLINE ENGINE 8.1 S INBOARD MODELS

APPLICATION / RATIO SELECTION

The propeller shaft speed is determined by engine speed and the transmission ratio. Every
boat has a best shaft speed that directly relates to boat speed. If propeller shaft speeds are
too high an inordinately small propeller must be used resulting in poor performance. If they
are too low then too large a propeller must be used. Fast boats do best with direct drive or
small reductions. Heavier and slower boats require corresponding greater ratios of
reduction. 100 rpm of propeller shaft speed for each mph of boat speed is a rough rule of
thumb for selecting the drive ratio.

COUPLING

The coupling is a flange type coupler (available through Quicksilver Accessories). All
coupler bolts must be SAE Grade 8 (Metric Grade 10.9) or better, with a shoulder (grip
length) long enough to pass through the face mating plane of couplers. All coupler bolts
must be torqued to 50 lb-ft (68 Nm).

ENGINE/PROPELLER SHAFT INSTALLATION ANGLE

The transmission and engine should be mounted so that the angle relative to horizontal is
as shown in the installation drawings. Refer to individual installation drawings for each
specific engine and transmission.

IMPORTANT: Relative to horizontal, never install the engine with the front (pulley
end) down.

IMPORT ANT: On all engines, a high angle of installation [front (pulley end) of engine
up] along with low transmission oil levels can permit transmission pump cavitation
on some models when operating in rough water.

PROPELLER SHAFT DIAMETER

The required propeller shaft diameter can vary significantly depending on the material used,
strut and bearing design, engine horsepower and shaft rpm. Information is available from
the propeller shaft manufacturer and in marine handbooks for selecting the proper diameter.
Sufficient shaft diameter is critical for durability and to minimize vibration. As a guideline,
the propeller shaft should be a minimum of 1/14 the diameter of the propeller.

VELVET DRIVE 72C TRANSMISSIONS

Velvet Drive 72C In-Line Only – Use of proper rotation propeller (specified on trans­mission output flange rotation decal) is critical since the transmission must be op­erated in forward gear selector position only to drive boat forward. If the wrong rota­tion propeller is installed and transmission is operated in reverse to propel the boat
forward, transmission failure WILL occur. On engines which are equipped with Vel­vet Drive In-line transmissions, a LH propeller is required.

CAUTION

Page 8 of 58

Installation Requirements

Engine Bed

Distance between starboard and port engine mount is 22-1/2 in. (572 mm). Engine bed must
position engine so that a minimum of 1/4 in. (6 mm) up and down adjustment still exists on
all 4 mounts after performing final engine alignment. This is necessary to allow for realigning
engine in the future.

NOTE: Although the engine mounts allow some adjustment, it is a good practice to ensure
that the front and rear mount locations in the vessel are in parallel planes. This may be
checked by tying a string from the left front mount location to the right rear mount location
and another from right front to left rear. The strings should touch where they cross

Engine Compartment

Boating standards (NMMA, ABYC) and Coast Guard regulations must be adhered
to when constructing the engine compartment.

Care must be exercised in the design and construction of the engine compartment. Seams
must be located so that any rain water that may leak through the seams, is directed away
from the air intake system.

GASOLINE ENGINE 8.1 S INBOARD MODELS

.

WARNING

VENTILATION

CAUTION

Water that runs onto the air intake may enter the engine and cause serious damage
to internal engine parts.

Engine compartments are being designed to be quieter. Insulation is the most common
material used to deaden the engine sound. Normally , the quieter the engine compartment,
the more insulation material used, resulting in less air space inside. The less air space inside
the engine compartment, the hotter the inside air temperature. Attention must be given to
the air temperature while the engine is running or for a period of time after the engine is shut
off (heat soak). Refer to the following information on Engine Compartment Ventilation.

According to Boating standards (NMMA, ABYC and others) and Coast Guard regulations
the engine compartment ventilation system has multiple tasks. Included are the following:

• To supply the engine with combustion air.

• To maintain a low temperature in the engine compartment.

Fresh air should enter the engine compartment as low as possible and the heated air should
be discharged from the highest point.

When sufficient ventilation is not provided, too much heat can build-up inside of engine
compartment and cause vapor locking. The engine will not want to restart after it has been
shut of f for a short period of time. If it does restart, the engine will quit when given the throttle
to get the boat up on plane or to pull up a water skier.

For engines utilizing fuels containing alcohol and the newer reformulated gasolines (Refer
to OEM Service Bulletin 95-2) proper ventilation is more critical to prevent vapor locking.

If a separate air shaft (or similar) is used to provide engine compartment ventilation or
additional ventilation, care must be taken to prevent seawater and spray from entering it.

Page 9 of 58

GASOLINE ENGINE 8.1 S INBOARD MODELS

COMBUSTION AIR REQUIREMENTS

Engine compartments with natural draft ventilation must have vent openings of sufficient
size and location to accomplish the tasks previously outlined.

IMPORTANT: The size of ventilation openings must be increased if any auxiliary
equipment is located in the engine compartment.

The combustion air requirement (per engine) for the specified engines at WOT are given
in the chart below:

Combustion Air Requirements (Per Engine)

TEMPERATURE

Model

8.1S HO 726 ft3/min. (0.342 m3/sec) 6.0 ft

8.1S Horizon 657 ft3/min.(.3 m3/sec.) 6.0 ft

Engine Air Requirements at

WOT

Engine Physical Volume

3

(170 l)

3

(170 l)

The pressure differential between outside and inside the engine compartment must not
exceed the following value.

Maximum Pressure Differential at WOT

2 in. (51 mm) of water (measured with a manometer)

Air temperatures inside the engine compartments have been measured in excess of
200° F (82° C). The long term effect to fuel system components running at these
excessive temperatures is not known.

According to specification SAE J1223 for Marine Carburetors:
“The carburetor shall be capable of operation throughout an ambient (air temperature)

range from +20° to +176° F (–7° to +80° C) without failure.”
Carburetors, throttle body injection (TBI) units and components for multi-port EFI systems

used by Mercury MerCruiser meet this specification.
Under the hottest outside air temperature condition at which the boat will be operated, the

air temperature inside the engine compartment, measured at the flame arrestor, should not
exceed 176 ° F (80° C). Also, the temperature of the fuel being supplied to the engine should
not exceed 110° F (43° C) at any location between the fuel tank and the engine’s fuel pump.

Since many factors influence engine compartment temperature, temperature measure­ments should always be carried out. Test as follows:

Page 10 of 58

TESTING

GASOLINE ENGINE 8.1 S INBOARD MODELS

NOTE: The boat being tested shall be a standard production boat fitted as it would be for
delivery to a dealer.

NOTE: Temperature test meter used shall be of the type that can be read without opening
the engine cover.

IMPORT ANT: During the test, in Step 1., engine compartments are to remain closed.
No outside air is to be forced into the engine compartment during the test and the
bilge blower should not be running.

1. Engine Running and Heat Soak Test:
a. Use 1 meter and 2-3 thermocouples. Place one thermocouple at the flame arrestor

to measure the inlet air temperature.

b. Place the second thermocouple at the fuel pump to measure the inlet fuel tempera-

ture.

c. A third thermocouple is needed if the fuel supply line between the tank and the fuel

pump is higher than the fuel pump. Place the third thermocouple at the highest point
of the supply line to measure the temperature of the fuel at that point.

2. Start engine and operate until engine is at normal operating temperature.

3. Operate engine at 1500 rpm (in NEUTRAL gear) for 15 minutes. Record temperature
readings at 5 minute intervals.

4. After 15 minutes at 1500 rpm, shut off engine and continue to record temperature
readings at 5 minute intervals for the next 45 minutes.

5. After the 45 minute heat soak test, start engine and idle (in NEUTRAL gear) for 20
minutes. Continue to record temperature readings at 5 minute intervals.

IMPORTANT: If the temperature at any location exceeds specifications, the engine
compartment will need additional ventilation until temperatures remain below these
specifications.

Page 11 of 58

GASOLINE ENGINE 8.1 S INBOARD MODELS

Exhaust System

It is the responsibility of the boat manufacturer or installing dealer to properly lo­cate the engine and install the exhaust system. Improper installation may allow wa­ter to enter the exhaust manifolds and combustion chambers and severely damage
the engine. Damage caused by water in the engine will not be covered by Mercury
MerCruiser Warranty, unless this damage is the result of defective parts.

Determine if exhaust elbow risers are required, by taking measurements “a” and “b,” with
boat at rest in the water and maximum load aboard. Subtract “b” from “a” to find “c.” If “c”
is less than specified in chart, select appropriate size exhaust elbow riser kit, and exhaust
extension kit if applicable, that will correctly position exhaust elbow.

CAUTION

Model

8.1S HO

8.1 Horizon

“c” Must Be 15 in. (381 mm) or More

“c” = “a” Minus “b”

b

d

a

c

77642

When designing and installing exhaust system, it is very important that the following points
be taken into consideration:

• System layout and construction must prevent cooling system discharge water from flow­ing back into engine and also must prevent seawater from entering engine via exhaust
system.

• The exhaust hoses and pipes must not be higher than exhaust elbows at any point.

• The drop must be constant so that a low spot does not exist at any point in the exhaust

hose or pipe.

Page 12 of 58

GASOLINE ENGINE 8.1 S INBOARD MODELS

Continuous Downward Slope From Horizontal

Engine

Model

Installation

Minimum Maximum

Angle*

Down-Angle

Inboard

Down-Angle

Inboard

Down-Angle

Inboard
V-Drive

Inboard
V-Drive

Inboard
V-Drive

Inboard

* Fore - End of engine closest to bow of boat.

Fore End

Raised 2°

Fore End

Raised 4°

Fore End

Lowered 7°

Fore End

Lowered 2°

0° 9°

Fore End

Raised 3°

11°

13°

16°

2-5/16 in. (59 mm)

per 12 in. (305 mm)

2-3/4 in. (70 mm)

per 12 in. (305 mm)

3-7/16 in. (87 mm)

per 12 in. (305 mm)

7°

1-1/2 in. (38 mm)

per 12 in. (305 mm)

1-7/8 in. (48 mm)

per 12 in. (305 mm)

12°

2-1/2 in. (64 mm)

per 12 in. (305 mm)

21°

23°

26°

17°

19°

22°

4-5/8 in. (117 mm)

per 12 in. (305 mm)
5-1/16 in. (129 mm)

per 12 in. (305 mm)

5-7/8 in. (149 mm)

per 12 in. (305 mm)
3-11/16 in. (94 mm)

per 12 in. (305 mm)

4-1/8 in. (105 mm)

per 12 in. (305 mm)

4-7/8 in. (124 mm)

per 12 in. (305 mm)

• The first 18 in. (457 mm) of exhaust hose should drop the specified minimum relative to

horizontal. Thereafter, 3 ° of drop or 1/2 in. (13 mm) of drop per 12 in. (305 mm) relative to
horizontal is a MINIMUM requirement for the rest of the exhaust system.

• Exhaust hoses should not restrict the flow of discharge water from the elbow. The ex-

haust hose cannot be bent more than 5° relative to the exhaust elbow outlet as a hot spot
in the hose will occur and burn through.

• Exhaust outlet must be above the water line with boat at rest in the water and loaded

to capacity.

• System must not cause excessive back pressure when measured 10 in. (254 mm) aft

of the exhaust elbow outlets. Back pressure MUST NOT exceed 2 psi (14 kPa). Mini­mum exhaust hose sizes are given in the following chart:

Minimum Exhaust Outlet Hose Size

Model Single Outlet Dual Outlet

ALL 5 in. (127 mm) 4 in. (102 mm)

• Exhaust hoses must be secured at each connection with 2 hose clamps.

• An exhaust resonator is included with all 496 cid / 8.1L engines. Installation of this kit is

required on 496 MAG and 496 MAG HO sterndrive engines with a through the transom
or through the hull exhaust. MerCruiser strongly recommends the use of this kit on all
other models.

Page 13 of 58

GASOLINE ENGINE 8.1 S INBOARD MODELS

• The exhaust resonator is positioned with the inside flat surface at the preferred distance
of 17 in. (432 mm) from the front edge of the exhaust hose but no closer than 2 in. (51
mm) to the exhaust outlet on sterndrives. The 17 in. (432 mm) dimension can be re­duced, if necessary, to a MINIMUM of 13 in. (330 mm). This dimension must be the same
on both exhaust outlets.

c

a

a

b

a

e

d

e

b

e

d

c

a

g

g

f

b

f

c

c

a a

b

e

f

e

d

75768

g

a-Exhaust Resonator
b-Exhaust Hose
c-Dimension to Inside Flat Surface Of Resonator Approximately 17 in. (432 mm)
d-No Less Than 2 in. (51 mm) Between Collector And Resonator
e-Clamp - Positioned Around Center of Resonator

f-Exhaust Muffler

g-Collector

Page 14 of 58

GASOLINE ENGINE 8.1 S INBOARD MODELS

NOTE: A kit is available, when applicable, to reduce from the 4 in. (102 mm) to 3 in. (76 mm).
Refer to the Quicksilver Accessories Guide, for kit part number.

c

Typical Continuously Sloping Exhaust Line

a-Exhaust Elbow
b-Exhaust Hose Or Pipe
c-Muffler (If Equipped)
d-Waterline

b

b

a

d

a

d

71774

g

c

e

Typical Waterlift Muffler Exhaust System

a-Vent Line [1/4 in. (6 mm)]
b-Transom
c-Water Line
d-Exhaust Hose
e-Drain Valve

f-Water Lift Muffler

g-Exhaust Elbow

f

71775

CAUTION

Avoid severe engine damage. A 1/4 in. (6 mm) vent hose must be run from the high­est point in the seawater system to the exhaust pipe after the water lift muffler to
break the vacuum and prevent water from back-filling the engine.

Page 15 of 58

GASOLINE ENGINE 8.1 S INBOARD MODELS

Fuel Delivery System

Boating standards (NMMA, ABYC, etc.) and Coast Guard regulations must be
adhered to when installing fuel delivery system.

The main concern of a boat’s fuel system is safety; this must be achieved through a
technically sound installation and constant inspection.

The fuel system, from the filler pipe to the fuel pump is the same, in principle, for all boats.
The fuel tank is an integrated component of the boat. Refer to the special information on

service and maintenance, which you have received from the tank manufacturer.
Only a few points related to function and safety are listed here [Refer to boating standards

(NMMA, ABYC) and Coast Guard regulations for complete guidelines]:

• All connections should be on the upper side of the tank.

• The drain plug at the lowest point on the tank serves to permit the removal of water and

sediment.

• The tank breather pipe must have an inner diameter of at least 1/2 in. (13 mm) and must
be fitted with a swan neck to prevent water from entering the tank.

It is recommended that the exact route and length of the fuel lines be established at the first
installation of the engine to prevent problems later in connecting them to the engine.

WARNING

All fuel lines must be well secured. The holes where the lines run through the bulkheads
should be carefully rounded off, or protected with rubber grommets. This prevents damage
to the lines from abrasion.

The following, but not limited to the following, additional fuel connection related points, must
be considered [Refer to boating standards (NMMA, ABYC) and Coast Guard regulations for
complete guidelines]:

1. Fuel tank should be mounted below carburetor level (if possible) or gravity feed may
cause carburetor fuel inlet needle to unseat, and flooding may result.

2. The maximum measured vacuum at the engine’s fuel inlet must not exceed 2 in. Hg (6.9
kPa) at 650, 3000, full throttle rpm and back at idle rpm.

IMPORTANT: Vacuum reading higher than specified can cause vapor locking with
some of today’s fuels. It can also cause poor engine performance because of fuel
starvation.

3. Fuel pickup should be at least 1 in. (25 mm) from the bottom of fuel tank, to prevent
picking up impurities.

4. Fuel lines used must be Coast Guard approved (USCG Type A1).

Page 16 of 58

Diameter of fittings and lines must not be smaller than 3/8 in. (10 mm) I.D. on 496 cid / 8.1L
engines.

5. On Multi-Engine Installations: It is best to use a fuel pickup and supply line for each

engine. If a single fuel pickup and supply line is used, fittings and line must not be smaller
than 1/2 in. (13 mm) I.D.

6. Larger diameter (than previously specified) lines and fittings must be used on

installations requiring long lines or numerous fittings.

7. Fuel lines should be installed free of stress and firmly secured to prevent vibration and/or

chafing.

8. Sharp bends in fuel lines should be avoided.

9. A flexible fuel line must be used to connect fuel supply line to fuel inlet fitting on engine,

to absorb deflection when engine is running.

SPECIAL INFORMATION ABOUT ELECTRIC FUEL PUMPS

CAUTION

The electric fuel pump and factory installed water separating fuel filter have been
carefully designed to function properly together . Do not install additional fuel filters
and/or water separating fuel filters between fuel tank and engine.

GASOLINE ENGINE 8.1 S INBOARD MODELS

The installation of additional filters may cause:

• Fuel Vapor Locking

• Difficult Warm-Starting

• Piston Detonation Due to Lean Fuel Mixture

• Poor Driveability

WARNING

Avoid gasoline fire or explosion. Improper installation of brass fittings or plugs into
fuel pump or fuel filter base can crack casting and/or cause a fuel leak.

IMPORTANT: The following information is provided to ensure proper installation of
brass fittings or plugs installed into fuel pump or fuel filter base:

• Use #592 Loctite Pipe Sealant with Teflon on threads of brass fittings or plugs. DO

NOT USE TEFLON TAPE.

• Brass fittings or plugs should first be threaded into fuel pump or fuel filter base

until finger tight.

• Fittings or plugs should then be tightened an additional 1-3/4 to 2-1/4 turns using

a wrench. DO NOT overtighten.

• T o prevent overtightening when installing a fuel line, the brass fittings should be

held with a suitable wrench as fuel line connectors are tightened securely.

Page 17 of 58

GASOLINE ENGINE 8.1 S INBOARD MODELS

Battery

IMPORTANT: Boating industry standards (BIA, ABYC), federal standards and Coast
Guard regulations must be adhered to when installing a battery. Be sure the battery
cable installation meets the pull test requirements and that positive battery terminal
is properly insulated in accordance with regulations.

IMPORTANT: Engine electrical system is negative (–) ground. It is recommended
(required in some states) that battery be installed in an enclosed case. Refer to
regulations for your area.

Select a battery that meets all of the following specifications:

• 12-volt marine type.

• Tapered post connector or side terminal connectors. Do not use a battery with wing nut

connectors.

• Reserve battery capacity rating of at least:

Engine (cyl./type)

V8 MPI 496 (8.1) 650 cca/825 mca/150Ah

MULTIPLE EFI ENGINE BATTERY PRECAUTIONS

NOTE: All references to EFI models apply to EFI and MPI Engines. The following precau­tions apply to all EFI models.

NOTE: All references to ECM apply to all engine control modules

Situation
Alternators: Alternators are designed to charge the battery that supplies electrical power

to the engine that the alternator is mounted on. When batteries for two different engines are
connected, one alternator will supply all of the charging current for both batteries. Normally,
the other engine’s alternator will not be required to supply any charging current.

EFI Electronic Control Module (ECM): The ECM requires a stable voltage source. During
multiple engine operation, an onboard electrical device may cause a sudden drain of voltage
at the engine’s battery. The voltage may go below the ECM’s minimum required voltage.
Also, the alternator on the other engine may now start charging. This could cause a voltage
spike in the engine’s electrical system.

In either case, the ECM could shut off. When the voltage returns to the range that the ECM
requires, the ECM will reset itself. The engine will now run normally. This ECM shut down
usually happens so fast that the engine appears to have an ignition miss.

cid (l)

Minimum Required Cranking

Battery Size

Recommendations
Batteries: Boats with multi-engine EFI power packages require each engine be connected

to its own battery. This ensures that the engine’s Electronic Control Module (ECM) has a
stable voltage source.

Battery Switches: Battery switches should always be positioned so each engine is running
off its own battery . DO NOT operate engines with switches in BOTH or ALL position. In an
emergency, another engine’s battery can be used to start an engine with a dead battery.

Page 18 of 58