Yamaha C40 Manual

							 
Maintenance 
46 
4. Once a month, check the specific gravity
of the electrolyte and recharge as re-
quired to prolong battery life. 
EMU28450 
Cleaning the outboard motor 
After use, wash the exterior of the outboard
motor with fresh water. Flush the cooling
system with fresh water.
NOTE:
 
For cooling system flushing instructions, see 
page 43. 
EMU28460 
Checking painted surface of motor 
Check the motor for scratches, nicks, or flak-
ing paint. Areas with damaged paint are
more likely to corrode. If necessary, clean
and paint the areas. A touch-up paint is avail-
able from your Yamaha dealer. 
EMU28486 
Periodic maintenance
WARNING
 
EWM01070  
Be sure to turn off the engine when you
perform maintenance unless otherwise
specified. If you or the owner is not famil-
iar with machine servicing, this work
should be done by your Yamaha dealer or 
other qualified mechanic.
Maintenance, replacement, or repair of
the emission control devices and sys-tems may be performed by any marine
engine repair establishment or individual.
All warranty repairs, however, including
those to the emission control system,
must be performed by an authorized
Yamaha marine dealership. 
A service manual is available for purchase
through your Yamaha dealer for owners who
have the mechanical skills, tools, and other
equipment necessary to perform mainte-
nance not covered by this owner’s manual. 
EMU28510 
Replacement parts 
If replacement parts are necessary, use only
genuine Yamaha parts or parts of the same
type and of equivalent strength and materi-
als. Any part of inferior quality may malfunc-
tion, and the resulting loss of control could
endanger the operator and passengers.
Yamaha genuine parts and accessories are
available from your Yamaha dealer.
ZMU03223
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Maintenance 
47 
EMU28522 
Maintenance chart 
Frequency of maintenance operations may be adjusted according to the operating condi-
tions, but the following table gives general guidelines. Refer to the sections in this chapter for
explanations of each owner-specific action.
NOTE:
 
When operating in salt water, turbid or muddy water, the engine should be flushed with clean 
water after each use.
The “” symbol indicates the check-ups which you may carry out yourself.
The “” symbol indicates work to be carried out by your Yamaha dealer. 
Item ActionsInitial Every
10 hours 
(1 month)50 hours 
(3 
months)100 
hours (6 
months)200 
hours (1 
year)  
Anode(s) (external)Inspection / replace-
ment
Anode(s) (internal)Inspection / replace-
ment
Battery Inspection / charging
Cooling water pas-
sagesCleaning
Cowling clamp Inspection
Fuel filter (can be dis-
assembled)Inspection / cleaning
Fuel system Inspection
Fuel tank (Yamaha por-
table tank)Inspection / cleaning
Gear oil Change
Greasing points Greasing
Idling speed (carbure-
tor models)Inspection
Power trim and tilt unit Inspection
Propeller and cotter pinInspection / replace-
ment
Shift link / shift cable Inspection / adjustment
ThermostatInspection / replace-
ment
Throttle link / throttle 
cable / throttle pick-up 
timingInspection / adjustment✩✦✯✬✤✲✲✣ ✧✪ 	
 


 
						

							 
Maintenance 
48
Water pumpInspection / replace-
ment
Oil pump Inspection / adjustment
Oil tank water drain Inspection / cleaning
Spark plug(s)Cleaning / adjustment / 
replacement 
Item ActionsInitial Every
10 hours 
(1 month)50 hours 
(3 
months)100 
hours (6 
months)200 
hours (1 
year)
✩✦✯✬✤✲✲✣ ✧✫ 	
 


 
						

							 
Maintenance 
49 
EMU28931 
Greasing 
Yamaha marine grease (Water resistant grease) 
40, 50 
EMU28952 
Cleaning and adjusting spark plug
WARNING
 
EWM00560  
When removing or installing a spark plug,
be careful not to damage the insulator. A
damaged insulator could allow external
sparks, which could lead to explosion or 
fire. 
The spark plug is an important engine com-
ponent and is easy to inspect. The condition
of the spark plug can indicate something
about the condition of the engine. For exam-
ple, if the center electrode porcelain is very
white, this could indicate an intake air leak or
carburetion problem in that cylinder. Do not
attempt to diagnose any problems yourself.
Instead, take the outboard motor to a
ZMU03414
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Maintenance 
50 
Yamaha dealer. You should periodically re-
move and inspect the spark plug because
heat and deposits will cause the spark plug
to slowly break down and erode. If electrode
erosion becomes excessive, or if carbon and
other deposits are excessive, you should re-
place the spark plug with another of the cor-
rect type.
Before fitting the spark plug, measure the
electrode gap with a wire thickness gauge;
adjust the gap to specification if necessary.
When fitting the plug, always clean the gas-
ket surface and use a new gasket. Wipe off
any dirt from the threads and screw in the
spark plug to the correct torque.
NOTE:
 
If a torque-wrench is not available when youare fitting a spark plug, a good estimate of
the correct torque is 1/4 to 1/2 a turn past fin-
ger-tight. Have the spark plug adjusted to the
correct torque as soon as possible with a 
torque-wrench. 
EMU28962 
Checking fuel system
WARNING
 
EWM00060  
Gasoline and its vapors are highly flam-
mable and explosive. Keep away from
sparks, cigarettes, flames, or other 
sources of ignition.
WARNING
 
EWM00910  
Leaking fuel can result in fire or explo-
sion. 
 
Check for fuel leakage regularly. 
 
If any fuel leakage is found, the fuel
system must be repaired by a qualified
mechanic. Improper repairs can make 
the outboard unsafe to operate. 
Check the fuel lines for leaks, crack, or mal-
function. If a problem is found, your Yamaha
dealer or other qualified mechanic should re-
pair it immediately. Standard spark plug:
40TR B7HS-10
50TR B8HS-10 
1. Spark plug gap
2. Spark plug I.D. mark (NGK) 
Spark plug gap:
0.9–1.0 mm (0.035–0.039 in)
Spark plug torque:
25.0 Nm (18.4 ft-lb) (2.55 kgf-m)✩✦✯✬✤✲✲✣ ✣ 	
 


 
						

							 
Maintenance 
51 
Checkpoints 
 
Fuel system parts leakage 
 
Fuel line joint leakage 
 
Fuel line cracks or other damage 
 
Fuel connector leakage 
EMU28980 
Inspecting fuel filter
WARNING
 
EWM00310  
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. 
 
Do not perform this procedure on a hot
or running engine. Allow the engine to
cool. 
 
There will be fuel in the fuel filter. Keep
away from sparks, cigarettes, flames or
other sources of ignition. 
 
This procedure will allow some fuel to
spill. Catch fuel in a rag. Wipe up anyspilled fuel immediately. 
 
The fuel filter must be reassembled
carefully with the O-ring, filter cup, and
hoses in place. Improper assembly or
replacement could result in a fuel leak,
which could result in a fire or explosion 
hazard. 
EMU29001 
Cleaning fuel filter 
1. Remove the nut holding the fuel filter as-
sembly if equipped.
2. Unscrew the filter cup, catching any
spilled fuel in a rag.
3. Remove the filter element, and wash it in
solvent. Allow it to dry. Inspect the filter
element and O-ring to make sure they
are in good condition. Replace them if
necessary. If any water is found in the
fuel, the Yamaha portable fuel tank or
other fuel tanks should be checked and
cleaned.
ZMU03126
 
1. Nut
ZMU03127
1
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Maintenance 
52 
4. Reinstall the filter element in the cup.
Make sure the O-ring is in position in the
cup. Firmly screw the cup onto the filter
housing.
5. Attach the filter assembly to the bracket
so that the fuel hoses are attached to the
filter assembly.
6. Run the engine and check the filter and
lines for leaks. 
EMU29041 
Inspecting idling speed
WARNING
 
EWM00451  
 
Do not touch or remove electrical parts
when starting or during operation. 
 
Keep hands, hair, and clothes away
from the flywheel and other rotating 
parts while the engine is running.
CAUTION:
 
ECM00490  
This procedure must be performed while
the outboard motor is in the water. A
flushing attachment or test tank can be 
used. 
A diagnostic tachometer should be used for
this procedure. Results may vary dependingon whether testing is conducted with the
flushing attachment, in a test tank, or with the
outboard motor in the water.
1. Start the engine and allow it to warm up
fully in neutral until it is running smooth-
ly.
NOTE:
 
Correct idling speed inspection is only possi-
ble if the engine is fully warmed up. If not
warmed up fully, the idle speed will measure
higher than normal. If you have difficulty ver-
ifying the idle speed, or the idle speed re-
quires adjustment, consult a Yamaha dealer 
or other qualified mechanic.
2. Verify whether the idle speed is set to
specification. For idle speed specifica-
tions, see page 42. 
EMU29061 
Checking water in engine oil tank 
A translucent water drain hose is connected
from the bottom of the oil tank to the filler
neck. If water or foreign matter collects in this
hose, consult a Yamaha dealer. 
EMU29112 
Checking wiring and connectors 
 
Check that each grounding wire is properly
secured. 
 
Check that each connector is engaged se- 
1. Filter cup
2. Filter element
3. Filter housing
4. O-ring
ZMU02079
1 4
2
3
 
1. Drain hose
2. Filler neck side
12
ZMU04989
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Maintenance 
53 
curely. 
EMU29120 
Exhaust leakage 
Start the engine and check that no exhaust
leaks from the joints between the exhaust
cover, cylinder head, and body cylinder. 
EMU29130 
Water leakage 
Start the engine and check that no water
leaks from the joints between the exhaust
cover, cylinder head, and body cylinder. 
EMU29162 
Checking power trim and tilt / power 
tilt system
WARNING
 
EWM00430  
 
Never get under the lower unit while it
is tilted, even when the tilt support lever
is locked. Severe injury could occur if
the outboard motor accidentally falls. 
 
Make sure no one is under the outboard 
motor before performing this test. 
1. Check the power trim and tilt unit / the
power tilt unit for any sign of oil leaks.2. Operate each of the power trim and tilt
switches / the power tilt switches on the
remote control and engine bottom cowl-
ing (if equipped) to check that all switch-
es work.
3. Tilt the outboard motor up and check
that the trim and tilt rod / the tilt rod is
pushed out completely.
4. Check that the trim and tilt rod / the tilt
rod is free of corrosion or other flaws.
5. Tilt the outboard motor down. Check
that the trim and tilt rod / the tilt rod oper-
ates smoothly.
NOTE:
 
Consult your Yamaha dealer if any operation 
is abnormal. 
EMU29171 
Checking propeller
WARNING
 
EWM00321  
You could be seriously injured if the en-
gine accidentally starts when you are
near the propeller. 
 
Before inspecting, removing, or install-
ing the propeller, remove the spark
plug caps from the spark plugs. Also,
place the shift control in neutral, turn
the main switch to “” (off) and re-
ZMU03240
 
1. Trim and tilt rod
2. Tilt support lever
12
ZMU03417
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Maintenance 
54 
move the key, and remove the lanyard
from the engine stop switch. Turn off
the battery cut-off switch if your boat
has one. 
 
Do not use your hand to hold the pro-
peller when loosening or tightening the
propeller nut. Put a wood block be-
tween the anti-cavitation plate and the
propeller to prevent the propeller from 
turning. 
Checkpoints 
 
Check each of the propeller blades for
wear, erosion from cavitation or ventila-
tion, or other damage. 
 
Check the propeller shaft for damage. 
 
Check the splines / shear pin for wear or
damage. 
 
Check for fish line tangled around the pro-
peller shaft. 
 
Check the propeller shaft oil seal for dam-
age.
NOTE:
 
If the shear pin equipped: it is designed to
break if the propeller hits a hard underwater
obstacle to help protect the propeller and
drive mechanism. The propeller will then
spin freely on the shaft. If this happens, the 
shear pin must be replaced. 
EMU30660 
Removing the propeller 
EMU29194 
Spline models 
1. Straighten the cotter pin and pull it out
using a pair of pliers.
2. Remove the propeller nut, washer, and
spacer (if equipped).
ZMU01896
ZMU01897
 
1. Cotter pin
2. Propeller nut
3. Washer
4. Spacer
ZMU03131
1
2
3
5 64
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Maintenance 
55 
3. Remove the propeller and thrust wash-
er. 
EMU30670 
Installing the Propeller 
EMU29231 
Spline models
CAUTION:
 
ECM00340  
 
Be sure to install the thrust washer be-
fore installing the propeller, otherwise
the lower case and propeller boss
could be damaged. 
 
Be sure to use a new cotter pin and
bend the ends over securely. Otherwise
the propeller could come off during op- 
eration and be lost. 
1. Apply Yamaha marine grease or a cor-
rosion resistant grease to the propeller
shaft.
2. Install the spacer (if equipped), thrust
washer, and propeller on the propeller
shaft.
3. Install the spacer (if equipped) and the
washer. Tighten the propeller nut to the
specified torque.
4. Align the propeller nut with the propeller
shaft hole. Insert a new cotter pin in the
hole and bend the cotter pin ends.
NOTE:
 
If the propeller nut does not align with the
propeller shaft hole after tightening to the
specified torque, tighten the nut further to 
align it with the hole. 
EMU29281 
Changing gear oil
WARNING
 
EWM00800  
 
Be sure the outboard motor is securely
fastened to the transom or a stable
stand. You could be severely injured if
the outboard motor falls on you. 
 
Never get under the lower unit while it
is tilted, even when the tilt support lever
or knob is locked. Severe injury could
occur if the outboard motor accidental- 
ly falls. 
1. Tilt the outboard motor so that the gear
oil drain screw is at the lowest point pos-
sible.
2. Place a suitable container under the
gear case.
3. Remove the gear oil drain screw.
NOTE:
 
If the magnetic gear oil drain screw
equipped: remove all metal particles from 
5. Propeller
6. Thrust washer 
1. Gear oil drain screw
2. Oil level plug
ZMU03133
2
1
✩✦✯✬✤✲✲✣