Yamaha 115 C Service Manual

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4-10
EMU01202
CLEANING AND ADJUSTING SPARK
PLUG
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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
component and is easy to inspect. The
condition of the spark plug can indicate
something about the condition of the
engine. For example, if the center elec-
trode 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
Yamaha dealer. You should periodically
remove 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 replace the
spark plug with another of the correct
type.
Before fitting the spark plug, measure the
electrode gap with a wire thickness
gauge; adjust the gap to specification if
necessary.
Standard spark plug:
Refer to “SPECIFICATIONS”, page 4-1.
Spark plug gap:
Refer to “SPECIFICATIONS”, page 4-1
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When fitting the plug, always clean the
gasket 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
you are fitting a spark plug, a good esti-
mate of the correct torque is 1/4 to 1/2 a
turn past finger-tight. Have the spark plug
adjusted to the correct torque as soon as
possible with a torque-wrench.
1Spark plug gap
2Spark plug I.D. mark (NGK)
903022
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Spark plug torque:
Refer to “SPECIFICATIONS”, page 4-1.
Initial of spark plug 
Plug wrench size
I.D. mark
B 21 mm (13/16 in.)
C/BK 16 mm (5/8 in.)
D 18.3 mm (23/32 in.)
EMU16350
CHECKING TOP COWLING
Check the fitting of the top cowling by
pushing it with both hands.
If the fitting is loose have it repaired by a
Yamaha dealer.
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4-12
EMK38010
CHECKING FUEL SYSTEM
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Gasoline (petrol) and its vapors are high-
ly flammable and explosive. Keep away
from sparks, cigarettes, flames or other
sources of ignition.
Check the fuel line for leaks, cracks, or mal-
functions. If any problem is found, it should
be repaired immediately by Yamaha dealer
or other qualified mechanic.
Checking points
8Fuel system parts leakage.
8Fuel hose joint leakage.
8Fuel hose cracks or other damage.
8Fuel connector leakage.
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Leaking fuel can result in fire or explo-
sion.
8Check for fuel leakage regularly.
8If any fuel leakage is found, the fuel
system must be repaired by a qualified
mechanic.
Improper repairs can make the out-
board unsafe to operate.
106031
106032
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V6
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EMK50011
CLEANING FUEL FILTER
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Gasoline (petrol) is highly flammable, and
its vapors are flammable and explosive.
8If you have any question about properly
doing this procedure, consult your
Yamaha dealer.
8Do not perform this procedure on a hot
or running engine. Allow the engine to
cool.
8There will be fuel in the fuel filter. Keep
away from sparks, cigarettes, flames or
other sources of ignition.
8This procedure will allow some fuel to
spill. Catch fuel in a rag. Wipe up any
spilled fuel immediately.
8The fuel filter must be reassembled
carefully with O-ring, filter cup, and
hoses in place. Improper assembly can
result in a fuel leak, which could result
in a fire or explosion hazard.
EMU09782
1) Remove the nut holding the fuel filter
assembly if equipped.
2) Unscrew the filter cup 1, catching
any spilled fuel in a rag.
3) Remove the filter element 2, and
wash it in solvent. Allow it to dry.
Inspect the filter element and O-ring
3to make sure they are in good con-
dition. 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.
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 4.
207031
000983
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er
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4-14
EMU09912
INSPECTING IDLING SPEED
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8Do not touch or remove electrical parts
when starting or during operation.
8Keep hands, hair and clothes away
from flywheel and other rotating parts
while engine is running.
cC
This procedure must be performed while
the outboard motor is in the water. A
flushing attachment or test tank can also
be used.
A diagnostic tachometer should be used
for this procedure. Results may vary
depending on whether testing is conduct-
ed 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
smoothly. If the outboard motor is
mounted on a boat, be sure the boat
is tightly moored.
2) Verify whether the idle speed is set to
specification. For idle speed specifica-
tions, see “Specifications” in this
chapter.
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.
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4-15
NOTE:
Correct idling speed inspection is only
possible if the engine is fully warmed up.
If not warmed up fully, the idle speed will
measure higher than normal. If you have
difficulty verifying the idle speed, or the
idle speed requires adjustment, consult a
Yamaha dealer or other qualified mechan-
ic.
213021
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EMK56010
CHECKING WATER TRAP UNDER
ENGINE OIL TANK
There is a trap at the bottom of the engine
oil tank. If water or foreign matter is visible
in this trap, consult a Yamaha dealer.
1Trap
2Engine oil tank
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EMU01329
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 proper amper-
age.
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Be sure to use the specified fuse. An
incorrect fuse or a piece of wire may
allow excessive current flow. This could
cause electrical system damage and a fire
hazard.
NOTE:
If the new fuse blows again immediately,
consult a Yamaha dealer.
1Fuse holder
2Fuse (20A/30A)
EMK78010
CHECKING WIRING AND
CONNECTORS
1) Check that each grounding wire is prop-
erly secured.
2) Check that each connector is engaged
securely.
EXHAUST LEAKAGE
Start the engine and check that no exhaust
leaks from the joints between the exhaust
cover, cylinder head and crank case.
WATER LEAKAGE
Start the engine and check that no water
leaks from the joints between the exhaust
cover, cylinder head and crank case.
205034
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205026*
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413012
V4
V6
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EMU00366
GREASING
Yamaha marine grease
(Water resistant grease)
V4
103061
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4-18
EMU00366
GREASING
Yamaha marine grease
(Water resistant grease)
V6
103062
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4-19
EML02011*
CHECKING POWER TRIM AND TILT
SYSTEM
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8Never get under the lower unit while it
is tilted, even when the tilt-support
lever is locked. Severe injury could
occur if the outboard accidentally falls.
8Make sure no one is under the out-
board before performing this test.
1)  Check the power trim and tilt unit for
any sign of oil leaks.
2) Operate each of the power trim and
tilt switches on remote control and
engine bottom cowling (If equipped)
to check that all switches work.
3) Tilt up the motor and check that the
tilt rod and trim rods are pushed out
completely.
4) Use the tilt-support lever to lock the
motor in the UP position. Operate the
tilt down switch briefly so the motor
is supported the tilt-support lever.
5) Check that the tilt rod and trim rods
are free of corrosion or other flaws.
6) Activate the tilt-down switch until the
trim rods have gone completely into
the cylinders.
7) Activate the trim-up switch until the
tilt rod is fully extended. Unlock the
tilt-support lever.
8) Operate the motor to tilt down. Check
that the tilt rod and trim rods operate
smoothly.
NOTE:
If any operation is abnormal, consult a
Yamaha dealer.
411024
Recommended fluid; Yamaha power
trim & tilt fluid or ATF (DEXRON-
II).
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