O.S. Engines 21XM User Manual

It is of vital importance, before attempting to
operate your engine, to read the general
'SAFETY INSTRUCTIONS AND WARNINGS'
section on pages 2-3 of this booklet and to
strictly adhere to the advice contained
therein.

Also, please study the entire contents of

•

this instruction manual, so as to familiarize
yourself with the controls and other
features of the engine.

Keep these instructions in a safe place so

•

that you may readily refer to them whenever
necessary.

It is suggested that any instructions

•

supplied with the model radio control
equipment, etc., are accessible for checking
at the same time.

CONTENTS

SAFETY INSTRUCTIONS AND WARNINGS ABOUT YOUR O.S. ENGINE
FITTING THE GLOWPLUG, INSTALLATION OF THE CARBURETTOR
BASIC ENGINE PARTS
PIPING, INSTALLATION, LINKAGES
FUEL AND GLOWPLUG
FLEXIBLE DRIVE SHAFT, PROPELLER, BEFORE STARTING THE ENGINE
ADJUSTING THE CARBURETTOR, REALIGNMENT OF MIXTURE CONTROL VALVE
STARTING
RUNNING-IN (''Breaking-in'')
ADJUSTMENT,CARBURETTOR CLEANLINESS
CARE AND MAINTENANCE
TROUBLE SHOOTING WHEN THE ENGINE FAILS TO START
EXPLODED VIEW
PARTS LIST
CARBURETTOR EXPLODED VIEW & PARTS LIST
THREE VIEW DRAWING AND SPECIFICATION

2~3

4
5
6
7
8
9

10

11

12~13

14
15
16
17
18
19

1

SAFETY INSTRUCTIONS AND
WARNINGS ABOUT YOUR
O.S. ENGINE

Remember that your engine is not a " toy ", but a highly
efficient internal-combustion machine whose power is
capable of harming you, or others, if it is misused.
As owner, you, alone, are responsible for the safe
operation of your engine, so act with discretion and care at
all times.
If at some future date, your O.S. engine is acquired by
another person, we would respectfully request that these
instructions are also passed on to its new owner.

The advice which follows is grouped under two headings

■

according to the degree of damage or danger which
might arise through misuse or neglect.

WARNINGS

These cover events which might involve serious (in
extreme circumstances, even fatal ) injury.

NOTES

These cover the many other possibilities, generally less
obvious sources of danger, but which, under certain
circumstances, may also cause damage or injury.

WARNINGS

Never touch, or allow any object to come

•

into contact with, the rotating propeller.
Model engine fuel is poisonous. Do not

•

allow it to come into contact with the eyes
or mouth. Always store it in a clearly
marked container and out of the reach
of children.

Model engine fuel is also highly flammable.

•

Keep it away from an open flame,
excessive heat, sources of sparks, or
anything else which might ignite it.
Do not smoke or allow anyone else to
smoke, near to it.

Never operate your engine in an enclosed space.

•

Model engines, like automobile engines, exhaust
deadly carbon-monoxide. Run your engine only in an
open area.

Model engines generate considerable

•

heat. Do not touch any part of your engine
until it has cooled. Contact with the
muffler(silencer), cylinder head or exhaust
header pipe, in particular, may result in a
serious burn.

2

NOTES

●

This engine was designed for model boats.
Do not attempt to use it for any other purpose.

●

Mount the engine in your model securely, following
the manufacturers' recommendations, using
appropriate screws and locknuts.

●

Fit an effective silencer(muffler).
Frequent close exposure to a noisy exhaust
(especially in the case of the most powerful high­speed engines) may eventually impair your hearing
and such noise is also likely to cause annoyance to
others over a wide area.

●

For their safety, keep all onlookers (especially
small children) well back (at least 12 feet or 4
metres) when preparing your model for running.

●

Take care that the glowplug clip or battery leads do
not come into contact with the propeller or any
other rotating parts. Also check the security of the
linkage to the throttle arm.

●

When starting your engine, use an electric
starter.The wearing of safety glasses is also
strongly recommended.

●

When handling the boat immediately prior to
launching, be especially cautious. Keep the
propeller and other rotating parts away from you.

●

Adjust the throttle linkage so that the engine stops
when the throttle stick and trim lever on the
transmitter are fully retarded. Alternatively, the
engine may
supply.

●

Warning! lmmediately after a glowplug-ignition

Never try to stop the engine physically.

be stopped by cutting off the fuel

engine has been run and is still warm, conditions
sometimes exist whereby it is just possible for the
engine to fire if the glowplug battery is accidentally
reconnected.

3

The O.S. MAX-21XM is a high-performance
water-cooled outboard marine engine for small
and medium-size radio-controlled outboard
boats. It is of sturdy construction and designed
for easy maintenance. It is not necessary to
readjust the linkage when the installation angle
to the hull is changed.
A tilt mount is supplied as standard. Also, a
carbon-fibre propeller is included.

FITTING THE GLOWPLUG

Fit washer to glowplug and insert
carefully into cylinder-head, making
sure that it is not cross-threaded before
tightening firmly.

Glow plug

Washer

INSTALLATION OF THE CARBURETTOR

NOTE

This engine rotates clockwise. Do not force it to

•

turn counter-clockwise.
With this engine, the piston will feel tight at the

•

top of its stroke when the engine is cold. This is
normal. The piston and cylinder are designed to
achieve a perfect running clearance when they
reach their normal running temperatures.

We do not recommend running your boat on the

•

sea, or in any other saltwater environment.
Under such conditions, it is difficult to prevent
the engine from becoming corroded and,
eventually, inoperative.

As delivered, this engine has its carburettor lightly fitted into
its intake boss. Secure it as follows.

1.

Loosen the retainer screw and rotate the carburettor to its
proper position in the intake boss.

2.

The carburettor is aligned vertically and sealed against air
leaks by a heatproof rubber gasket between the
carburettor body and the rim of the intake boss. Therefore,
press the carburettor firmly down into the intake boss while
rotating the retainer screw.
Turn the screw gently until it stops, then tighten a further
90˚.

Note:
The two-piece retainer is designed to pinch the carburettor
from both sides. Do not overtighten.

4

BASIC ENGINE PARTS

Carburettor(OS TYPE 20J)

Needle-Valve

Water-Cooled Cylinder Head

E-2050 Silencer

Water Inlet Tube

Exhaust Outlets

Cooling Water Pickup

Flywheel(OS No.2J)

Mixture Control Screw
Crankcase

Throttle Lever

Throttle Linkage Bracket

Steering Arm

Transom Mounting Plate

Oil Transfer Tube

Cavitation Plate

Outboard Unit Lower Housing

Carbon-Reinforced Propeller

Skeg

5

PIPING

Connect the water inlet tube (L=170mm) and oil transfer pipe
(L=65mm) securely as shown on page 5. In the event of either
tube becoming damaged, it should be replaced with best
quality 5.5mm OD✕2.5mm ID silicone tubing.

Note : When cutting silicone tubing.....

Silicone tubing

Use knife or razor blade. Do not use wire cutters or pliers

If you should need to clean out silicone tubes, use methanol or glow-fuel, not gasoline.

INSTALLATION

The face of the mounting plate is precision machined flat.
Make sure that the hull's transom is also flat. The adjacent
hull structures should be as rigid as possible so that the
engine will be able to develop its full performance. Use 4mm
steel screws, such as Allen type socket head cap screws, with
locknuts or lockwashers for bolting the engine to the hull. For
extra security, apply LOCTITE to the screw threads to prevent
nuts vibrating loose.

LINKAGES

Steering Linkage

Use a high-torque servo, preferably with dual pushrods as
shown below.(A single pushrod will bend easily which results
in poor steering accuracy.)

Steering Servo

Steering Arm

Throttle Linkage

Use flexible 'Bowden' type cable having a 3mm OD outer
sleeve. Secure one end of the sleeve to the engine, by means
of the throttle linkage bracket supplied, and the other end to
any appropriate part of the hull structure immediately sur­rounding the throttle servo.(See sketch) If the two ends are
not secured in this way, steering the boat will upset throttle
control. Make sure that no strain is imposed on the throttle
cable when steering fully left or right. Adjust the throttle link­age so that the throttle can be fully closed to stop the engine
prior to lifting the boat from the water.(If necessary, consult
your R/C system handbook for setting up linkage in relation to
transmitter stick movement.)

6

Secure

Linkage Bracket

3mm OD Outer Pipe

Throttle Servo

Reminder!

Model engine fuel is poisonous. Do not allow it to
come into contact with the eyes or mouth. Always
store it in a clearly marked container and out of the
reach of children.

Model engine fuel is also highly flammable. Keep it
away from naked flame, excessive heat, sources of
sparks, or anything else which might ignite it. Do not
smoke, or allow anyone else to smoke, near to it.

FUEL

Use only top quality commercial model two-stroke engine fuel.
For consistent performance and long engine life, it is essential
to use fuel containing AT LEAST 18%(volumetric ratio)best­quality lubricant. This engine is designed to run on both low
and high nitromethane content fuels, i.e. from mild mixtures
containing a few percent of nitromethane, up to high-speed racing
fuels containing 30%, or more, of nitromethane. Generally, power
output is increased
content of the fuel is increased. As a starting point, we recommend
a fuel containing 10% nitromethane, changing to a fuel
containing more nitro if necessary. When the nitro content of the
fuel is increased or the brand of fuel is changed, it is advisable to
run the engine with a richer needle-valve setting, initially, so
that the optimum setting for the new fuel may be rechecked as
described in the RUNNING-IN paragraph.

-

up to a certain point-as the nitromethane

GLOWPLUG

The O.S. No.8 glowplug is recommended and one is supplied
with this engine. The MAX-21XM may not always run so well
with other types of plug.

The role of the glowplug

With a glowplug engine, ignition is initiated by the application
of a 1.5-volt power source. When the battery is disconnected,
the heat retained within the combustion chamber remains
sufficient to keep the plug filament glowing, thereby continuing
to keep the engine running. Ignition timing is 'automatic':
under reduced load, allowing higher rpm, the plug becomes
hotter and, appropriately, fires the fuel/air charge earlier;
conversely, at reduced rpm, the plug becomes cooler and
ignition is retarded.

Glowplug life

Particularly in the case of very high performance engines,
glowplugs must be regarded as expendable items. However,
plug life can be extended and engine performance maintained
by careful use, i.e.:

7

●

Fit a plug suitable for the engine (e.g. OS No.8).

●

Use fuel containing a moderate percentage of nitromethane
unless essential for racing events.

●

Do not run the engine too lean and do not leave the battery
connected while adjusting the needle.

When to replace the glowplug -

Apart from when actually burned out, a plug may need to be
replaced because it no longer delivers its best performance,
such as when:

●

Filament surface has roughened and turned white.

●

Filament coil has become distorted.

●

Foreign matter has adhered to filament or plug body has
corroded.

●

Engine tends to cut when idling.

●

Starting qualities deteriorate.

FLEXIBLE DRIVE SHAFT

If, due to accidental damage or wear, the flexible drive shaft
(see p.16) should require replacement, proceed as follows.
(Note: a wise precaution is to have a spare flexible shaft on
hand for such emergencies.)

1.

With aid of the correct sized screwdrivers and hexagon
keys, separate the complete lower end (outboard unit
assembly) from the power-head and remove all parts
necessary to give access to the flexible drive shaft. This
has squared ends that fit into the PTO shaft at the power­head and the propeller shaft at the bottom end. Note that
the propeller shaft bearing has a left-hand thread.

2.

Remove the flexible drive shaft and its sleeve and if any deb­ris is found in the sleeve, wash it out with fuel or alcohol be­fore greasing the full length of the new shaft and reinserting
it into the sleeve.

Make sure that the ends of the new shaft fit properly into the

3.
PTO shaft and propeller shaft and that the new flexible shaft
rotates smoothly.
Then replace the curved side plate, cavitation plate,etc. and
re-unite the power-head with the lower assembly. Gently turn
the flywheel to check that the propeller rotates smoothly be­fore tightening assembly screws.

PROPELLER

The MAX-21XM's special carbon-fibre propeller has a
diameter of 42mm and a P/D ratio of 1.2. If any other propeller
is substituted, make sure that it is properly balanced.

Never touch, or allow any object to come into contact
with, the rotating propeller and do not crouch over the
engine when it is running.

BEFORE STARTING THE ENGINE

●

The rapid changes of hull attitude that occur when a fast
boat is operating in choppy water, especially when the fuel
tank is located at some distance from the carburettor,
means that fuel ''head''at the carburettor jet can vary quite
considerably, causing the engine to run erratically or stop.
Therefore, it is advisable to use a moderately pressurized
fuel system.

8

●

Before starting the engine for the first run of the day,
remove the glowplug and check the engine by rotating the
flywheel by hand. It should rotate smoothly. Now turn the
engine with an electric starter until fuel is drawn into the
carburettor. At first, rotation may feel 'sticky' due to oily
residue remaining within the engine. The engine should
rotate freely after fresh mixture has been drawn into the
working parts.

●

Check the glowplug. If the plug element is distorted, off­center, or has a white appearance, engine performance
may be below par.
Replace the plug if necessary.

●

When re-starting the engine, turn the flywheel by hand, as
before (but without removing the glowplug) to make sure
that there is nothing unusual, before energizing the glowplug
and applying the starter.

WARNING!
Never attempt to turn the engine with the starter if the engine
is over-primed with fuel or flooded with corrosion-inhibiting oil.
To do so is likely to seriously damage the working parts.

ADJUSTING THE CARBURETTOR

Two adjustable controls are provided on this carburettor.

●

The Needle-Valve:

For adjusting the mixture strength when the throttle is fully
open.

●

The Mixture Control Screw:

For adjusting the mixture strength at idling speeds, to ob­tain steady idling and smooth acceleration to mid speeds.

REALIGNMENT OF MIXTURE CONTROL VALVE

In the course of making carburettor adjustments, it is just
possible that the Mixture Control Valve may be inadvertently
screwed in or out too far and thereby moved beyond its
effective adjustment range. (Refer to sketch, p.10, top left.)
Its basic setting can be reestablished as follows:
The basic (factory) setting is as shown in the main sketch, i.e.
with the shoulder portion 'A' exactly at a tangent to the throttle
rotor hole.
To return the Mixture Control Valve to its original position, first
screw in the Mixture Control Valve, while looking into the rotor
hole. Then gradually unscrew the Mixture Control Valve until
'A' is precisely tangential to the rotor hole (i.e. so that 'A' and
'B' are superimposed) as in the main sketch.

9

Nozzle

Throttle Rotor Hole

Mixture Control Valve

(Mixture Control Screw)

STARTING

Set the needle-valve. Turn the needle clockwise slowly,

◆

without forcing, until it stops.
Then, reopen the needle-valve 2-1/2turns counterclock­wise.

Mark

Open

◆

Open the throttle very slightly:

Turn needle-valve clockwise to close
(for leaner mixture)

Close

Turn needle-valve counterclockwise to
open (for richer mixture)

◆

Heat the glowplug by connecting the battery leads.

◆

Make sure that the direction of
rotation of the electric starter is
correct, namely, clockwise.

Clockwise­rotation

If necessary, reverse leads on
battery to provide clockwise rotation.

◆

Bring the starter into contact with the
flywheel and depress the starter
switch for one or two seconds.
Repeat if necessary. When the engine fires, withdraw the
starter immediately.

Warning:

Do not apply the starter to a flooded engine and never
place your finger over the carburettor intake when using
the starter. This may cause an hydraulic lock and bend
the connecting-rod.

◆

Adjusting the needle-valve: adjust the needle-valve to its
optimum setting only while actually running your boat on the
water.

◆

To stop the engine, fully close the throttle to cut off air
supply.

This is to avoid unnecessarily
high revolutions when the engine
starts.

10

RUNNING-IN (''Breaking-in'')

For long life and high-performance, every engine needs to be
properly 'run-in' or 'broken-in'. There are several running-in
methods, but the following is suitable for use with the MAX­21XM.

1.

Turn the Needle-Valve clockwise slowly and gently until it
stops. This is the fully closed position. Do not use force to
turn the Needle-Valve beyond this point. Now reopen the
Needle two-and-one-half turns. (The set-screw on the
Needle-Valve knob may be used as a reference mark.)

Set the throttle at the starting position, (i.e. very slightly

2.
opened from idling position) and start the engine.

The propeller blades are extremely sharp. Never touch, or
allow any object to come into contact with, the rotating
propeller and do not crouch over the engine when it is
running. Do not touch any part of the power-head until it
has cooled. Contact with the muffler (silencer) or cylin­der, also, may result in a serious burn.

WARNING!
It is vitally important to set the throttle at the correct starting
position before starting the engine. If the engine is allowed to
run under 'no-load' conditions, it will speed up to extremely
high revolutions even at part-throttle settings which may
result in serious damage.
Be careful not to put excessive load on the steering servo when
starting the engine with an electric starter. It is advisable to set
the steering fully left before applying an electric starter.

3.

It is necessary to warm up the engine by running it at
around the idling setting for a while after starting, as with
the engine of a full size boat. High r.p.m. operation without
warming up will shorten engine life or damage it.

Leaving the Needle-Valve set at the starting setting of 2-1/2

4.
turns open, run the boat several times with the throttle fully
open until at least three full tanks of fuel have been
consumed. (It should be noted that, at this stage, it may not
be possible for the engine to idle reliably because of the
over-rich setting of the Needle-Valve.)

This completes the initial running-in stage.

5.
For the remaining period of running-in, refer to the
adjustment procedures detailed later.
The boat will need to be run for about 10 tanks of fuel to
complete the running-in period.

Note!
If as a result of your boat being capsized, the engine
takes in water, remove the glowplug, invert the engine
and eject water by carefully turning the flywheel, first by
hand and then with the electric starter. Make every effort
to ensure that no water remains in the engine before
attempting to restart it, or it may be damaged by an
hydraulic lock.
To ensure that any traces of water (which may also cause
internal rusting if not dealt with)are flushed out, use an
appropriate water-displacing spray lubricant.

11

ADJUSTMENT

WARNING
Running the engine with the boat out of the water, with­out load and without cooling water, will seriously damage
it, due to overheating. Therefore, always lower the boat
into the water immediately after the engine has been star­ted, so as to prevent over-speeding and to allow cooling
water to be forced up to the cylinder-head. Having carried
out the initial running-in (''breaking-in'') procedure as de­scribed before, complete the running-in as follows:

Open the throttle slightly from the

1.
idling position and start the engine,
following the procedure described
previously.

Lower the boat into the water,

2.
gradually open the
the boat straight ahead for 20 to 30 metres at full throttle.
Now return the model and close the needle-valve 20 to 30
Repeat the run, taking note of the improvement in speed.

Continue with further runs, gradually closing the needle-

3.
valve (20 to 30˚at a time) until no further increase in speed
is obtained.

If the needle-valve is closed beyond the optimum setting,

4.
the model will slow down, accompanied by visibly
diminished exhaust smoke. In this case, immediately
throttle down and return the model to shore. Re-open the
needle-valve approximately one-half turn and repeat the
runs until the optimum needle setting is found.

:

throttle and run

Fig.-1

˚

Aim to have the model achieving its highest performance

5.
after the engine has consumed about one litre of fuel.
Having found the optimum needle-valve setting, make a
note of the number of turns necessary to re-establish this
from the closed position.

With the engine run-in and the optimum needle-valve

6.
setting determined, the mixture control valve should be
checked as follows:

Launch the boat and gradually open the throttle to its fullest

7.
extent. If at this point, the engine puffs out a good deal of

smoke and does not accelerate smoothly and rapidly, it is a
sign that the idling mixture is too rich.
Therefore, turn the mixture control screw clockwise 45 to
60˚. Repeat the run and recheck the result.

If, on the other hand, the idling mixture is too lean, the

8.
engine is likely to speed up momentarily, then cut out
abruptly when the throttle is re-opened. In this case, first
turn the mixture control screw counter-clockwise 90˚to

.

make sure that the mixture has become richer, then make
incremental adjustments, each way, until an acceptable
balance between rich v.lean settings is achieved. Carry out
these adjustments patiently under actual running
conditions, until the engine responds quickly and positively
to throttle movements. Use a small screwdriver to adjust
the mixture control valve via its slotted screwhead in the
center of the outer end of the throttle rotor.

12

With the optimum mixture control valve position, light

9.
smoke is visible during high-speed running and engine
revolutions increase smoothly during acceleration.
Remember that, if the engine is operated with the fuel/air
mixture slightly too lean, it will overheat and run unevenly
or cut out. As with all engines, it is wise to set both valves
a little on the rich side of the best rpm setting, as a safety
measure.

When the best balance of mixture adjustments has been

10.
determined and, especially as the engine becomes fully
run-in, it will probably be found that the idling speed has
increased. Readjust the throttle opening by means of the
trim lever on the transmitter, so that the lowest idling
speed, without risk of stalling the engine, may be
obtained.

WARNING

:
For safety reasons, it is advisable to stop the engine
before carrying out adjustments to the Mixture Control
Screw.

:

Note
Once the correct carburettor settings have been

established, it should be unnecessary to alter them.
Such slight Needle-Valve readjustments as may be
required to compensate for variations in atmospheric
conditions will not normally affect the other two controls.
Slight readjustments may be necessary for optimum
performance if different types of fuel, glowplugs or
propellers are used.

CARBURETTOR CLEANLINESS

Proper functioning of the carburettor depends on its small fuel
orifices remaining clear.
The minute particles of foreign matter that are present in any
fuel, can partially obstruct these orifices and upset mixture
strength so that engine performance becomes erratic and
unreliable.
It is recommended that fuel is passed through a filter when
the tank is filled and that a good in-line filter is installed
between the fuel tank and carburettor and, furthermore, that
this filter is frequently cleaned to remove dirt and lint that
accumulate on the filter screen.
Finally, occasionally remove the needle-valve hol-der from the
carburettor as shown below and extract any remaining foreign
matter that may have lodged in the location shown.

Remove this with an
8mm spanner

Dirt and fibrous matter
mostly accumulate here

13

CARE AND MAINTENANCE

To ensure that you obtain long life and peak performance
from your engine, observe the follow-ing.

As previously observed, foreign matter in the fuel can

1

cause problems. Therefore:

●

rinse out the fuel tank with methanol or fuel before installing
it.

●

fit a fuel filter to the fuel delivery tube between tank and
carburettor.

●

fit a fuel filter to the outlet of your squeeze bottle,
pump inlet if you use a manual or electric pump.

●

do not leave your fuel container open need-lessly.

✽ O.S. 'Super-Filters' (large and small) are available, as op­tional extras,to deal with this problem. One of these filters, fit­ted to the outlet tube inside your refuelling container, will pre­vent the entry of foreign material into the fuel tank.

2

Do not forget to clean the filters regularly to remove dirt
and lint that accumulate on the filter screens.
Also, clean the carburettor itself occasionally.

3

At the end of each operating session, drain out any fuel
that may remain in the fuel tank. Afterwards, energize the
glowplug and try to restart the engine, to burn off any fuel
that may remain inside the engine. Repeat this procedure
until the engine fails to fire. Leaving fuel residues within
the engine can result in difficult starting after a period of
storage. It may also cause corrosion.

or to the

✽

To reduce such risks, it is helpful to inject some corrosion
inhibiting oil into the engine's air intake.
Rotate the engine many times to distribute the oil to all the
working parts.

4

Drain the water remaining in the water cooling head, and
wash out with methanol, then inject corrosion-inhibiting or
moisture-displacing oil.

5

When cleaning the exterior of the engine, use methanol or
kerosene. Do not use gasoline or any solvent that might
damage the silicone fuel tubing or any plastic parts of the
boat hull.

6

When the engine is not in use remove the glowplug and
rinse out the interior with kerosene (not gasoline), by
rotating the crankshaft. Shake out residue, then inject light
machine-oil through the plug hole again rotating the shaft
to distribute the protective oil to all working parts.

7

In the event of water having entered the cylinder,
crankcase, etc., refer to the procedures recommended in
the footnote to p.11.

Avoid unnecessary disassembly of your engine, but if

8

attention to the 21XM's flexible drive shaft appears
necessary, please refer to p.8.

14

TROUBLE SHOOTING WHEN THE ENGINE FAILS TO START

Four key points

For quick, reliable starting, the following four conditions are required.

1 Good compression. 2 Adequate "glow" at glowplug. 3 Correct mixture.

If the engine fails to start, or does not keep running after being started, check symptoms against the following chart and take
necessary corrective action. Note: The most common causes of trouble are marked with three asterisks, the less common

problems with one or two asterisks.

4 Sufficient electric starter rotating speed.

Symptom

Engine fails
to fire.

Engine fires
intermittently but
does not run.

Engine fires once or
twice, then fails to fire.

Engine starts but revol­utions decrease and en­gine eventually stops.

Engine starts, then
revolutions increase
and engine cuts out.

Engine stops when battery
leads are disconnected
after starting.

Factor

4

2

3

2
3

4
2

3
3

3

3
2

Cause

Sluggish rotation

★

Glowplug battery

★★

discharged.
Glowplug element is

★

burned out
Something wrong with

★

battery leads.
Engine "flooded"

★★

Insufficient fuel.

★

Incorrect heating of

★★

glowplug.
Excess fuel

★★

Sluggish rotation.

★

Glowplug battery

★★

discharged.

Insufficient fuel

★★

Mixture too rich.

★★★

Fuel not reaching the

★

engine.
Mixture too rich.

★★

Mismatch of glow plug

★

and fuel.

.....

.....

....

...

......

......

....

.......

.....

.....

....

......

....

......

....

Corrective action

Recharge the electric starter battery.
Recharge lead-acid cell or replace dry battery. (Note: An unused, or almost unused, dry battery

may sometimes be of insufficient capacity if it is "old stock".)
Replace glowplug. Check that applied voltage is not too high.
Check glowplug heating using other leads.
Close needle-valve fully and remove glowplug, Apply starter to pump out excess fuel. Re-start

engine.

Refer to p.9
Voltage too high or too low. Re-check and readjust referring to "BEFORE STARTING"
Continue to apply starter. If necessary disconnect battery from glowplug and leave for a few

minutes, then re-energize plug. If engine still does not start, remove glowplug and pump out excess
fuel.
Then re-start.

Recharge the electric starter battery.
Recharge lead-acid cell or replace dry battery.

(Note: An unused, or almost unused, dry battery may sometimes be of insufficient capacity if it is
"old stock".)

Refer to p.9
Close needle-valve half turn (180˚) and wait for several minutes, then re-start.

Make sure that tank is filled with fuel. Check that there is not something wrong with fuel tubing
(kinked or split). Check that carburettor is not clogged with dirt.

Close the needle-valve a little.
Change fuel or glowplug.

15

EXPLODED VIEW

1-1

N.+M3X10

23-F

1

N.+M4X8

C.M2.6X18

12

✽ Type of screw

C.M3X12

13-3

C.M2.6X18

11

11-1

13

6

9

7

8

10

13-2

13-1

C.M2.6X10

C…Cap Screw M…Oval Fillister-head Screw F…Flat Head Screw

18

C.M3X10

3

17

21
22

C.M2.6X8

2

N.M3X10

4

N.M3X12

14

15

16

23-B

19

20

N…Round Head Screw

5

23-E

25

23-C

23-D

S…Set Screw

23-C1

23-C2

23-A

F.M3X10

23

23-G

C.M4X12

23-J

23-H

23-I

C.M4X12

23-L

24

F.M3X8

23-K

23-M

16

PARTS LIST

No.

1

1-1

2
3
4
5
6
7
8

9
10
11

11-1

12
13

13-1
13-2
13-3

14
15
16
17
18

Code No.

7 1802 100
2 7721 700
4 1614 000
2 3851 000
2 3981 700
7 1532 000
2 5382 000
2 3805 000
2 3817 000
2 3906 000
2 3803 010
2 3841 000
2 4025 923
2 3913 000
2 3875 000
2 3875 300
2 2681 953
2 3875 400
2 3930 000
2 3852 000
2 3852 100
2 2631 019
2 3814 010

Description

Flywheel Assembly (No.2J)
Flywheel Nut
Crankshaft Ball Bearing ( Outer )
Crankcase
Carburettor Retainer
Throttle Linkage Bracket
Carburettor Type 20J
Connecting Rod
Piston Pin Retainer ( 2pcs.)
Piston Pin
Cylinder & Piston Assembly
Water-Cooled Head Assembly
Nipple No.2
Screw Set
E-2050 Silencer
Silencer Assembly Screw (4pcs.)
Nipple No.1
Silencer Fixing Screw ( 2pcs.)
Crankshaft Ball Bearing ( Inner )
Crankshaft
Power Take-Off Shaft
PTO Shaft Ball-Bearing ( Inner )
Gasket Set

No.

23-A
23-B

23-C
23-C1
23-C2

23-D

23-E

23-F

23-G

23-H

23-I

23-J
23-K
23-L

23-M

Code No.

19

2 3871 130

20

2 3861 000

21

2 2631 019

22

2 3852 200

23

2 3871 000
2 3871 100
2 3871 200
2 3873 010
2 3873 000
2 3873 100

2 3871 400

2 3810 000
2 3874 500
2 3874 100
2 3874 000
2 3874 200
2 3874 300
2 3871 300
4 5571 100
2 3871 700

24

2 2681 953

25

2 3870 000
7 1608 001

The specifications are subject to alteration for improvement without notice.

Description

Outboard Unit Fixing Screw (4pcs.)
Crankcase Rear Housing
PTO Shaft Ball-Bearing ( Outer )
PTO Shaft Nut
Outboard Unit Assembly
Lower Housing and Skeg
Side Plate
Flexible Drive Assembly
Flexible Drive Shaft
Flexible Drive Shaft Sleeve
Propeller Shaft Assembly
Propeller Nut
Steering Arm
Upper Swivel Bracket
Transom Mounting Plate
Lower Swivel Bracket
Swivel/Tilt Assembly
Cavitation Plate
Universal Nipple L3.5
Cooling Water Pickup
Nipple No.1
Marine Propeller
Glowplug No.8

17

CARBURETTOR EXPLODED VIEW & PARTS LIST

S.3X3

1-1

1

2

5

4

3-1

3

6

9

7

S.3X3

8-5

8-2

8-4

8

8-3

8-1

No.

1

1-1

2
3

3-1

4
5
6

Code No. Description

2 4981 405
2 6381 501
2 5381 203
2 6781 309
2 4881 824
2 6781 506
2 5382 100
2 5381 220

Throttle Lever Assembly
Set-screw
Carburettor Rotor
Mixture Control Valve
'' O '' Ring (2pcs.)
Rotor Spring
Carburettor Body
Rotor Guide Screw

No.

7
8

8-1
8-2
8-3
8-4
8-5

9

Code No. Description

2 2681 953
2 7881 900
2 4981 959
2 4981 837
2 6381 501
2 7381 940
2 6711 305
2 9015 019

Fuel Inlet
Needle Valve Assembly
Needle
'' O '' Ring (2pcs.)
Set-screw
Needle Valve Holder Assembly
Ratchet Spring
Carburettor Rubber Gasket

The specifications are subject to alteration for improvement without notice.

18

THREE VIEW DRAWING

SPECIFICATION

Displacement

■

Bore

■

Stroke

■

Practical R.P.M.

■

Power output

■

Weight

■

3.46 c.c. ( 0.211 cu.in.)

16.6 mm ( 0.654 in.)

16.0 mm ( 0.630 in.)
3,000~25,000 r.p.m.

1.3 bhp / 25,000r.p.m.
670g ( 23.6 oz.)

64

48.5

87

46

46

37.5

48.5

46

219

45 25

34.5

86

149.5
183

19

MEMO

20

E

C

R

I

P

S

I

Y

O

T

I

N

L

A

U

Q

D

E

L

L

A

U

Q

E

N

U

&

P

E

R

F

O

R

M

A

N

C

E

C

Copyright 2000 by O.S.Engines Mfg. Co., Ltd. All rights reserved. Printed in Japan.

E

S

T

A

B

L

I

S

H

I

N

G

T

H

D

E

R

S

A

T

D

A

N

E

C

N

E

L

L

E

C

X

E

F

O

S

6-15 3-Chome Imagawa Higashisumiyoshi-ku
Osaka 546-0003, Japan

TEL. [phone]

FAX. [phone]

URL : http://www.os-engines.co.jp

100101