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...

 
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...

 
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,...

 
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...

 
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....

 
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...

 
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...

 
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...

 
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...