Yamaha C40 Manual

							 
Maintenance 
56 
the screw before installing it.
4. Remove the oil level plug to allow the oil
to drain completely.
CAUTION:
 
ECM00710  
Inspect the used oil after it has been
drained. If the oil is milky, water is getting
into the gear case which can cause gear
damage. Consult a Yamaha dealer for re- 
pair of the lower unit seals.
NOTE:
 
For disposal of used oil consult your Yamaha 
dealer.
5. With the outboard motor in a vertical po-
sition, and using a flexible or pressur-
ized filling device, inject the gear oil into
the gear oil drain screw hole.
6. When the oil begins to flow out of the oil
level plug hole, insert and tighten the oil
level plug.
7. Insert and tighten the gear oil drain
screw. 
EMU29302 
Cleaning fuel tank
WARNING
 
EWM00920  
Gasoline is highly flammable, and its va-
pors are flammable and explosive. 
 
If you have any question about properly
doing this procedure, consult your
Yamaha dealer. 
 
Keep away from sparks, cigarettes,
flames, or other sources of ignition
when cleaning the fuel tank. 
 
Remove the fuel tank from the boat be-
fore cleaning it. Work only outdoors in
an area with good ventilation. 
 
Wipe up any spilled fuel immediately. 
 
Reassemble the fuel tank carefully. Im-
proper assembly can result in a fuel
leak, which could result in a fire or ex-
plosion hazard. 
 
Dispose of old gasoline according to lo- 
cal regulations. 
1. Empty the fuel tank into an approved
container.
2. Pour a small amount of suitable solvent
into the tank. Install the cap and shake
the tank. Drain the solvent completely.
3. Remove the screws holding the fuel joint
assembly. Pull the assembly out of the
tank.
4. Clean the filter (located on the end of the Recommended gear oil:
Hypoid gear oil SAE#90
Gear oil quantity:
430.0 cm 
3
 
 (14.54 US oz) (15.17 
Imp.oz)
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Maintenance 
57 
suction pipe) in a suitable cleaning sol-
vent. Allow the filter to dry.
5. Replace the gasket with a new one. Re-
install the fuel joint assembly and tighten
the screws firmly. 
EMU29312 
Inspecting and replacing anode(s) 
Yamaha outboard motors are protected from
corrosion by sacrificial anodes. Inspect the
external anodes periodically. Remove scales
from the surfaces of the anodes. Consult a
Yamaha dealer for replacement of external
anodes.
CAUTION:
 
ECM00720  
Do not paint anodes, as this would render 
them ineffective.
NOTE:
 
Inspect ground leads attached to external
anodes on equipped models. Consult a
Yamaha dealer for inspection and replace-
ment of internal anodes attached to the pow- 
er unit. 
EMU29320 
Checking battery (for electric start 
models)
WARNING
 
EWM00330  
Battery electrolytic fluid is dangerous; it
contains sulfuric acid and therefore is
poisonous and highly caustic.
Always follow these preventive mea-
sures: 
 
Avoid bodily contact with electrolytic
fluid as it can cause severe burns or
permanent eye injury. 
 
Wear protective eye gear when han-
dling or working near batteries.
Antidote (EXTERNAL): 
 
SKIN - Flush with water. 
 
EYES - Flush with water for 15 minutes
and get immediate medical attention.
Antidote (INTERNAL): 
 
Drink large quantities of water or milk
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Maintenance 
58 
followed by milk of magnesia, beaten
egg, or vegetable oil. Get immediate
medical attention.
Batteries also generate explosive hydro-
gen gas; therefore, you should always
follow these preventive measures: 
 
Charge batteries in a well-ventilated ar-
ea. 
 
Keep batteries away from fire, sparks,
or open flames (for example: welding
equipment, lighted cigarettes, and so
on.) 
 
DO NOT SMOKE when charging or han-
dling batteries.
KEEP BATTERIES AND ELECTROLYTIC 
FLUID OUT OF REACH OF CHILDREN.
CAUTION:
 
ECM00360  
 
A poorly maintained battery will quickly
deteriorate. 
 
Ordinary tap water contains minerals
harmful to a battery, and should not be 
used for topping up. 
1. Check the electrolyte level at least once
a month. Fill to the manufacturer’s rec-
ommended level when necessary. Top
up only with distilled water (or pure de-
ionized water suitable to use in batter-
ies).
2. Always keep the battery in a good stateof charge. Installing a voltmeter will help
you monitor your battery. If you will not
use the boat for a month or more, re-
move the battery from the boat and store
it in a cool, dark place. Completely re-
charge the battery before using it.
3. If the battery will be stored for longer
than a month, check the specific gravity
of the fluid at least once a month and re-
charge the battery when it is low.
NOTE:
 
Consult a Yamaha dealer when charging or 
re-charging batteries. 
EMU29331 
Connecting the battery
WARNING
 
EWM00570  
Mount the battery holder securely in a
dry, well-ventilated, vibration-free loca-
tion in the boat. Install a fully charged bat- 
tery in the holder.
CAUTION:
 
ECM01121  
 
Make sure the main switch (on applica-
ble models) is “” (off) before work-
ing on the battery. 
 
Reversal of the battery cables will dam-
age the electrical parts. 
 
Connect the red battery cable first
when installing the battery and discon-
nect the black battery cable first when
removing it. Otherwise, the electrical
parts can be damaged. 
 
The electrical contacts of the battery
and cables must be clean and properly
connected, or the battery will not start 
the engine. 
Connect the red battery cable to the POSI-
TIVE (+) terminal first. Then connect the
black battery cable to the NEGATIVE (-) ter-✩✦✯✬✤✲✲✣ ✫ 	
 


 
						

							 
Maintenance 
59 
minal. 
EMU29370 
Disconnecting the battery 
Disconnect the BLACK cable from the NEG-
ATIVE (-) terminal first. Then disconnect the
RED cable from the POSITIVE (+) terminal. 
EMU29390 
Checking top cowling 
Check the fitting of the top cowling by push-
ing it with both hands. If it is loose have it re-
paired by your Yamaha dealer. 
EMU29400 
Coating the boat bottom 
A clean hull improves boat performance. The
boat bottom should be kept as clean of ma-
rine growth as possible. If necessary, the
boat bottom can be coated with an anti-foul-ing paint approved for your area to inhibit
marine growth.
Do not use anti-fouling paint which includes
copper or graphite. These paints can cause
more rapid engine corrosion. 
1. Red cable
2. Black cable
3. Battery
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60 
Trouble Recovery 
EMU29424 
Troubleshooting 
A problem in the fuel, compression, or igni-
tion systems can cause poor starting, loss of
power, or other problems. This section de-
scribes basic checks and possible remedies,
and covers all Yamaha outboard motors.
Therefore some items may not apply to your
model.
If your outboard motor requires repair, bring
it to your Yamaha dealer.
If the engine trouble warning indicator is
flashing, consult your Yamaha dealer. 
Starter will not operate. 
Q. Is battery capacity weak or low?
A. Check battery condition. Use battery of
recommended capacity.
Q. Are battery connections loose or corrod-
ed?
A. Tighten battery cables and clean battery
terminals.
Q. Is fuse for electric start relay or electric cir-
cuit blown?
A. Check for cause of electric overload and
repair. Replace fuse with one of correct am-
perage.
Q. Are starter components faulty?
A. Have serviced by a Yamaha dealer.
Q. Is shift lever in gear?
A. Shift to neutral. 
Engine will not start (starter operates). 
Q. Is fuel tank empty?
A. Fill tank with clean, fresh fuel.
Q. Is fuel contaminated or stale?A. Fill tank with clean, fresh fuel.
Q. Is fuel filter clogged?
A. Clean or replace filter.
Q. Is starting procedure incorrect?
A. See page 30.
Q. Has fuel pump malfunctioned?
A. Have serviced by a Yamaha dealer.
Q. Are spark plug(s) fouled or of incorrect
type?
A. Inspect spark plug(s). Clean or replace
with recommended type.
Q. Are spark plug cap(s) fitted incorrectly?
A. Check and re-fit cap(s).
Q. Is ignition wiring damaged or poorly con-
nected?
A. Check wires for wear or breaks. Tighten
all loose connections. Replace worn or bro-
ken wires.
Q. Are ignition parts faulty?
A. Have serviced by a Yamaha dealer.
Q. Is engine stop switch lanyard not at-
tached?
A. Attach lanyard.
Q. Are engine inner parts damaged?
A. Have serviced by a Yamaha dealer. 
Engine idles irregularly or stalls. 
Q. Are spark plug(s) fouled or of incorrect
type?
A. Inspect spark plug(s). Clean or replace
with recommended type.✩✦✯✬✤✲✲✣ ✩✣ 	
 


 
						

							 
Trouble Recovery 
61 
Q. Is fuel system obstructed?
A. Check for pinched or kinked fuel line or
other obstructions in fuel system.
Q. Is fuel contaminated or stale?
A. Fill tank with clean, fresh fuel.
Q. Is fuel filter clogged?
A. Clean or replace filter.
Q. Have ignition parts failed?
A. Have serviced by a Yamaha dealer.
Q. Has warning system activated?
A. Find and correct cause of warning.
Q. Is spark plug gap incorrect?
A. Inspect and adjust as specified.
Q. Is ignition wiring damaged or poorly con-
nected?
A. Check wires for wear or breaks. Tighten
all loose connections. Replace worn or bro-
ken wires.
Q. Is specified engine oil not being used?
A. Check and replace oil as specified.
Q. Is thermostat faulty or clogged?
A. Have serviced by a Yamaha dealer.
Q. Are carburetor adjustments incorrect?
A. Have serviced by a Yamaha dealer.
Q. Is fuel pump damaged?
A. Have serviced by a Yamaha dealer.
Q. Is air vent screw on fuel tank closed?
A. Open air vent screw.
Q. Is choke knob pulled out?A. Return to home position.
Q. Is motor angle too high?
A. Return to normal operating position.
 
Q. Is carburetor clogged?
A. Have serviced by a Yamaha dealer.
Q. Is fuel joint connection incorrect?
A. Connect correctly.
Q. Is throttle valve adjustment incorrect?
A. Have serviced by a Yamaha dealer.
Q. Is battery cable disconnected?
A. Connect securely. 
Warning buzzer sounds or indicator
lights. 
Q. Is cooling system clogged?
A. Check water intake for restriction.
Q. Is engine oil level low?
A. Fill oil tank with specified engine oil.
Q. Is heat range of spark plug incorrect?
A. Inspect spark plug and replace it with rec-
ommended type.
Q. Is specified engine oil not being used?
A. Check and replace oil with specified type.
Q. Is engine oil contaminated or deteriorat-
ed?
A. Replace oil with fresh, specified type.
Q. Is oil filter clogged?
A. Have serviced by a Yamaha dealer.
Q. Has oil feed/injection pump malfunc-
tioned?✩✦✯✬✤✲✲✣ ✩✤ 	
 


 
						

							 
Trouble Recovery 
62 
A. Have serviced by a Yamaha dealer.
Q. Is load on boat improperly distributed?
A. Distribute load to place boat on an even
plane.
Q. Is water pump or thermostat faulty?
A. Have serviced by a Yamaha dealer.
Q. Is there excess water in fuel filter cup?
A. Drain filter cup. 
Engine power loss. 
Q. Is propeller damaged?
A. Have propeller repaired or replaced.
Q. Is propeller pitch or diameter incorrect?
A. Install correct propeller to operate out-
board at its recommended speed (r/min)
range.
Q. Is trim angle incorrect?
A. Adjust trim angle to achieve most efficient
operation.
Q. Is motor mounted at incorrect height on
transom?
A. Have motor adjusted to proper transom
height.
Q. Has warning system activated?
A. Find and correct cause of warning.
Q. Is boat bottom fouled with marine growth?
A. Clean boat bottom.
Q. Are spark plug(s) fouled or of incorrect
type?
A. Inspect spark plug(s). Clean or replace
with recommended type.Q. Are weeds or other foreign matter tangled
on gear housing?
A. Remove foreign matter and clean lower
unit.
Q. Is fuel system obstructed?
A. Check for pinched or kinked fuel line or
other obstructions in fuel system.
Q. Is fuel filter clogged?
A. Clean or replace filter.
Q. Is fuel contaminated or stale?
A. Fill tank with clean, fresh fuel.
Q. Is spark plug gap incorrect?
A. Inspect and adjust as specified.
Q. Is ignition wiring damaged or poorly con-
nected?
A. Check wires for wear or breaks. Tighten
all loose connections. Replace worn or bro-
ken wires.
Q. Have electrical parts failed?
A. Have serviced by a Yamaha dealer.
Q. Is specified fuel not being used?
A. Replace fuel with specified type.
Q. Is specified engine oil not being used?
A. Check and replace oil with specified type.
Q. Is thermostat faulty or clogged?
A. Have serviced by a Yamaha dealer.
Q. Is air vent screw closed?
A. Open the air vent screw.
Q. Is fuel pump damaged?
A. Have serviced by a Yamaha dealer.✩✦✯✬✤✲✲✣ ✩✥ 	
 


 
						

							 
Trouble Recovery 
63 
Q. Is fuel joint connection incorrect?
A. Connect correctly.
Q. Is heat range of spark plug incorrect?
A. Inspect spark plug and replace it with rec-
ommended type.
Q. Is high pressure fuel pump drive belt bro-
ken?
A. Have serviced by a Yamaha dealer.
Q. Is engine not responding properly to shift
lever position?
A. Have serviced by a Yamaha dealer. 
Engine vibrates excessively. 
Q. Is propeller damaged?
A. Have propeller repaired or replaced.
Q. Is propeller shaft damaged?
A. Have serviced by a Yamaha dealer.
Q. Are weeds or other foreign matter tangled
on propeller?
A. Remove and clean propeller.
Q. Is motor mounting bolt loose?
A. Tighten bolt.
Q. Is steering pivot loose or damaged?
A. Tighten or have serviced by a Yamaha
dealer. 
EMU29432 
Temporary action in 
emergency 
EMU29440 
Impact damage
WARNING
 
EWM00870  
The outboard motor can be seriouslydamaged by a collision while operating or
trailering. Damage could make the out- 
board motor unsafe to operate. 
If the outboard motor hits an object in the wa-
ter, follow the procedure below.
1. Stop the engine immediately.
2. Inspect the control system and all com-
ponents for damage. Also inspect the
boat for damage.
3. Whether damage is found or not, return
to the nearest harbor slowly and careful-
ly.
4. Have a Yamaha dealer inspect the out-
board motor before operating it again. 
EMU29462 
Replacing fuse 
If the fuse has blown on an electric start
model, open the fuse holder and replace the
fuse with a new one of the proper amperage.
WARNING
 
EWM00630  
Be sure to use the specified fuse. An in-
correct fuse or a piece of wire could allow
excessive current flow. This could cause 
electric system damage and a fire hazard.✩✦✯✬✤✲✲✣ ✩✦ 	
 


 
						

							 
Trouble Recovery 
64
NOTE:
 
Consult your Yamaha dealer if the new fuse 
immediately blows again. 
EMU29522 
Power trim and tilt / power tilt will not 
operate 
If the engine cannot be tilted up or down with
the power trim and tilt / the power tilt because
of a discharged battery or a failure with the
power trim and tilt unit / the power tilt unit, the
engine can be tilted manually.
1. Loosen the manual valve screw by turn-
ing it counterclockwise until it stops.
2. Put the engine in the desired position,then tighten the manual valve screw by
turning it clockwise. 
EMU29531 
Starter will not operate 
If the starter mechanism does not operate
(the engine cannot be cranked with the start-
er), the engine can be started with an emer-
gency starter rope.
WARNING
 
EWM01020  
 
Use this procedure only in an emergen-
cy and only to return to port for repairs. 
 
When the emergency starter rope is
used to start the engine, the start-in-
gear protection device does not oper-
ate. Make sure the remote control lever
is in neutral. Otherwise the boat could
unexpectedly start to move, which
could result in an accident. 
 
Attach the engine stop switch lanyard
to a secure place on your clothing, or
your arm or leg while operating. 
 
Do not attach the lanyard to clothing
that could tear loose. Do not route the
cord where it could become entangled,
preventing it from functioning. 
 
Avoid accidentally pulling the lanyard
during normal operation. Loss of en-
gine power means the loss of most
steering control. Also, without engine
power, the boat could slow rapidly. This
could cause people and objects in the
boat to be thrown forward. 
 
Be sure no one is standing behind you
when pulling the starter rope. It could
whip behind you and injure someone. 
 
An unguarded, rotating flywheel is very
dangerous. Keep loose clothing and
other objects away when starting the
engine. Use the emergency starter rope
only as instructed. Do not touch the fly- 
1. Fuse holder
2. Fuse (20 A)
3. Spare fuse (20 A)
1. Manual valve screw
12
3
ZMU03421
1
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Trouble Recovery 
65 
wheel or other moving parts when the
engine is running. Do not install the
starter mechanism or top cowling after
the engine is running. 
 
Do not touch the ignition coil, spark
plug wire, spark plug cap, or other elec-
trical components when starting or op-
erating the motor. You could get an 
electrical shock. 
EMU29573 
Emergency starting engine 
1. Remove the top cowling.
2. Disconnect the start-in-gear protection
cable from the starter, if equipped.
3. Remove the starter/flywheel cover after
removing the bolt(s).
4. Prepare the engine for starting. For fur-
ther information, see page 30. Be sure
the engine is in neutral and that the en-
gine stop switch lanyard lock plate is at-
tached to the engine stop switch. Themain switch must be “” (on), if
equipped.
5. Insert the knotted end of the emergency
starter rope into the notch in the flywheel
rotor and wind the rope several turns
around the flywheel clockwise.
6. Pull the rope slowly until resistance is
felt.
7. Give a strong pull straight out to crank
and start the engine. Repeat if neces-
sary.
ZMU03425
ZMU03139
ZMU03140
OFF
ZMU03541
ON
ZMU03429
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