Yamaha C40 Manual

							 
Basic components 
16 
EMU26151 
Power trim and tilt switch on bottom 
engine cowling 
The power trim and tilt switch is located on
the side of the bottom engine cowling. Press-
ing the switch “” (up) trims the outboard
motor up, then tilts it up. Pressing the switch
“” (down) tilts the outboard motor down
and trims it down. When the switch is re-
leased, the outboard motor will stop in its
current position.
WARNING
 
EWM01030  
Use the power trim and tilt switch located
on the bottom engine cowling only when
the boat is at a complete stop with the en-
gine off. Attempting to use this switch
while the boat is moving could increase
the risk of falling overboard and could
distract the operator, increasing the risk
of collision with another boat or an obsta- 
cle.
NOTE:
 
For instructions on using the power trim and 
tilt switch, see page 37. 
EMU26241 
Trim tab with anode 
The trim tab should be adjusted so that the
steering control can be turned to either the
right or left by applying the same amount of
force.
WARNING
 
EWM00840  
An improperly adjusted trim tab could
cause difficult steering. Always test run
after the trim tab has been installed or re-
placed to be sure steering is correct. Be
sure you have tightened the bolt after ad- 
justing the trim tab. 
If the boat tends to veer the left (port side),
turn the trim tab rear end to the port side “A”
in the figure. If the boat tends to veer the right
(starboard side), turn the trim tab end to the
starboard side “B” in the figure.
CAUTION:
 
ECM00840  
The trim tab also serves as an anode to
protect the engine from electrochemical
corrosion. Never paint the trim tab as it 
will become ineffective as an anode.
DOWNUP
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Basic components 
17 
EMU26261 
Trim rod (tilt pin) 
The position of the trim rod determines the
minimum trim angle of the outboard motor in
relation to the transom. 
EMU26340 
Tilt support lever for power trim and 
tilt or hydro tilt model 
To keep the outboard motor in the tilted up
position, lock the tilt support lever to the
clamp bracket. 
EMU26372 
Top cowling lock lever(s) (turn type) 
To remove the engine top cowling, turn the
lock lever(s) and lift off the cowling. When in-
stalling the cowling, check to be sure it fits
properly in the rubber seal. Then lock the
cowling again by returning the lever(s) to the
lock position. 
1. Trim tab
2. Bolt
A
B
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2
ZMU03357
 
1. Top cowling lock lever(s)
1. Top cowling lock lever(s)
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Basic components 
18 
EMU26470 
Tachometer 
This gauge shows the engine speed and has
the following functions. 
EMU26491 
Digital tachometer 
The tachometer shows the engine speed
and has the following functions.
NOTE:
 
All segments of the display will light momen-
tarily after the main switch is turned on and 
will return to normal thereafter.
NOTE:
 
The water separator and engine trouble
warning indicators only operate when the en-
gine is equipped with the appropriate func- 
tions. 
EMU26540 
Oil level indicators (three indicators 
2) 
The indicators on the gauge show the status
of the oil level. For details on how to read the
indicators, see page 29.
CAUTION:
 
ECM00030  
Do not operate the engine without oil. Se- 
rious engine damage will occur. 
EMU26550 
Oil level indicator (digital type) 
This indicator shows the engine oil level. If
the oil level falls below the lower limit, the
warning indicator will start to blink. For fur-
ther information, see page 21.
CAUTION:
 
ECM00030  
Do not operate the engine without oil. Se- 
1. Tachometer
2. Oil level indicator
1. Tachometer
2. Trim meter
3. Hour meter
4. Oil level indicator
5. Overheat warning indicator
6. Water separator warning indicator
ZMU04577
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2
6
7
2
4
9
8 5 31
ZMU01958
 
7. Engine trouble warning indicator
8. Set button
9. Mode button
1. Oil level indicators
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Basic components 
19 
rious engine damage will occur. 
EMU26581 
Overheat warning indicator (digital 
type) 
If the engine temperature rises too high, the
warning indicator will start to blink. For fur-
ther information on reading the indicator, see
page 20.
CAUTION:
 
ECM00050  
Do not continue to run the engine if the
overheat warning indicator is on. Serious 
engine damage will occur. 
EMU26610 
Trim meter 
This gauge shows the trim angle of your out-
board motor.
NOTE:
 
Memorize the trim angles that work best for
your boat under different conditions. Adjust
the trim angle to the desired setting with the 
power trim and tilt switch. 
EMU26620 
Trim meter (digital type) 
This meter shows the trim angle of your out-
board motor.
NOTE:
 
 
Memorize the trim angles that work best
for your boat under different conditions.
Adjust the trim angle to the desired using
the power trim and tilt switch. 
 
If the trim angle of your motor exceeds the
trim operating range, the top segment on 
the trim meter display will blink. 
EMU26650 
Hour meter (digital type) 
This meter shows the number of hours the 
1. Oil level indicator
1. Overheat warning indicator
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Basic components 
20 
engine has been run. It can be set to show
the total number of hours or the number of
hours for the current trip. The display can
also be turned on and off. 
 
Changing the display format 
 
Pressing the “” (mode) button chang-
es the display format in the following pat-
tern: 
 
Total hours 
→ 
Trip hours 
→ 
Display off 
 
Resetting the trip hours 
 
Simultaneously pressing the “” (set)
and “” (mode) buttons for more than
1 second while the trip hours are displayed
resets the trip counter to 0 (zero).
NOTE:
 
The total number of hours the engine has 
been run cannot be reset. 
EMU26801 
Warning system
CAUTION:
 
ECM00090  
Do not continue to operate the engine if a
warning device has activated. Consult
your Yamaha dealer if the problem can- 
not be located and corrected. 
EMU26814 
Overheat warning 
This engine has an overheat warning device.
If the engine temperature rises too high, the
warning device will activate. 
Activation of warning device 
 
The engine speed will automatically de-
crease to about 2000 r/min. 
 
If equipped with an overheat warning indi-
cator, it will light. 
 
The buzzer will sound (if equipped on the
tiller handle, remote control box, or main
switch panel).
If the warning system has activated, stop the
engine and check the cooling water inlet for
clogging.
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Basic components 
21 
EMU26845 
Oil level warning and oil filter 
clogging warning 
Oil injection models 
This engine has an oil level warning system.
If the oil level falls below the lower limit, the
warning system will activate. 
Activation of warning device 
 
Engine speed will automatically decrease
to about 2000 r/min. 
 
The oil level warning indicator will light. 
 
The buzzer will sound (if equipped on the
tiller handle, remote control box, or main
switch panel).
If the warning system has been activated,
stop the engine and check for the cause.
NOTE:
 
The warning for oil filter clogging is similar to
the warnings for low oil level and overheat-
ing. To make troubleshooting easier, check
for engine overheating first, then oil level, 
and finally oil filter clogging.
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Basic components 
22
1. Oil filter
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23 
Operation 
EMU26901 
Installation
CAUTION:
 
ECM00110  
Incorrect engine height or obstructions
to smooth water flow (such as the design
or condition of the boat, or accessories
such as transom ladders or depth finder
transducers) can create airborne water
spray while the boat is cruising. Severe
engine damage may result if the motor is
operated continuously in the presence of 
airborne water spray.
NOTE:
 
During water testing check the buoyancy of
the boat, at rest, with its maximum load.
Check that the static water level on the ex-
haust housing is low enough to prevent wa-
ter entry into the powerhead, when water
rises due to waves when the outboard is not 
running. 
EMU26910 
Mounting the outboard motor
WARNING
 
EWM00820  
 
Overpowering a boat could cause se-
vere instability. Do not install an out-
board motor with more horsepower
than the maximum rating on the capac-
ity plate of the boat. If the boat does not
have a capacity plate, consult the boat
manufacturer. 
 
The information presented in this sec-
tion is intended as reference only. It is
not possible to provide complete in-
structions for every possible boat and
motor combination. Proper mounting
depends in part on experience and the 
specific boat and motor combination.
WARNING
 
EWM00830  
Improper mounting of the outboard mo-
tor could result in hazardous conditions
such as poor handling, loss of control, or
fire hazards. Observe the following: 
 
For permanently mounted models, your
dealer or other person experienced in
proper rigging should mount the motor.
If you are mounting the motor yourself,
you should be trained by an experi-
enced person. 
 
For portable models, your dealer or oth-
er person experienced in proper out-
board motor mounting should show 
you how to mount your motor. 
Mount the outboard motor on the center line
(keel line) of the boat, and ensure that the
boat itself is well balanced. Otherwise the
boat will be hard to steer. For boats without
a keel or which are asymmetrical, consult
your dealer. 
EMU26930 
Mounting height (boat bottom) 
To run your boat at optimum efficiency, the
water resistance (drag) of the boat and out-
board motor must be made as little as possi-
ble. The mounting height of the outboard 
1. Center line (keel line)
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Operation 
24 
motor greatly affects the water resistance. If
the mounting height is too high, cavitation
tends to occur, thus reducing the propulsion;
and if the propeller tips cut the air, the engine
speed will rise abnormally and cause the en-
gine to overheat. If the mounting height is too
low, the water resistance will increase and
thereby reduce engine efficiency. Mount the
outboard motor so that the anti-cavitation
plate is in alignment with the bottom of the
boat.
NOTE:
 
 
The optimum mounting height of the out-
board motor is affected by the boat/motor
combination and the desired use. Test
runs at different heights can help deter-
mine the optimum mounting height. Con-
sult your Yamaha dealer or boat
manufacturer for further information on de-
termining the proper mounting height. 
 
For instructions on setting the trim angle of 
the outboard motor, see page 35. 
EMU26970 
Clamping the outboard motor 
1. Place the outboard motor on the tran-
som so that it is positioned as close to
the center as possible. Tighten the tran-
som clamp screws evenly and securely.
Occasionally check the clamp screws
for tightness during operation of the out-
board motor because they could be-come loose due to engine vibration.
WARNING
 
EWM00640  
Loose clamp screws could allow the out-
board motor to fall off or move on the
transom. This could cause loss of control
and serious injury. Make sure the tran-
som screws are tightened securely. Oc-
casionally check the screws for tightness 
during operation. 
2. If the engine restraint cable attachment
is equipped on your engine, an engine
restraint cable or chain should be used.
Attach one end to the engine restraint
cable attachment and the other to a se-
cure mounting point on the boat. Other-
wise the engine could be completely lost
if it accidentally falls off the transom.
3. Secure the clamp bracket to the transom
using the bolts provided with the out-
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Operation 
25 
board (if packed). For details, consult
your Yamaha dealer.
WARNING
 
EWM00650  
Avoid using bolts, nuts or washers other
than those contained in the engine pack-
aging. If used, they must be of at least the
same quality of material and strength and
must be tightened securely. After tighten-
ing, test run the engine and check their 
tightness. 
EMU27020 
Breaking in engine 
Your new engine requires a period of break-
in to allow mating surfaces of moving parts to
wear in evenly. Correct break-in will help en-
sure proper performance and longer engine
life.
CAUTION:
 
ECM00140  
 
Failure to follow the break-in procedure
could result in reduced engine life or
even severe engine damage. 
 
Premix fuel must be used during break-
in in addition to oil in the oil injection 
system. 
EMU27060 
Gasoline and engine oil mixing chart 
(50:1)
CAUTION:
 
ECM00150  
Be sure to mix gasoline and oil complete-
ly, otherwise the engine may be dam- 
aged. 
EMU30310 
Procedure for oil injection models 
Run the engine under load (in gear with a
propeller installed) as follows.
1. First 10 minutes:
Run the engine at the lowest possible
speed. A fast idle in neutral is best.
2. Next 50 minutes:
Do not exceed half throttle (approxi-
mately 3000 r/min). Vary engine speed
occasionally. If you have an easy-plan-
ing boat, accelerate at full throttle onto
plane, then immediately reduce the
throttle to 3000 r/min or less.
3. Second hour:
Accelerate at full throttle onto plane,
then reduce engine speed to three-quar-
ter throttle (approximately 4000 r/min).
Vary engine speed occasionally. Run at
full throttle for one minute, then allow
about 10 minutes of operation at three-
quarter throttle or less to let the engine 
1. Bolts
ZMU03185
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1
 
1. : Gasoline
2.  : Engine oil✩✦✯✬✤✲✲✣ ✥