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4-11
EMU01035
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.
67F-9-16-4 11/3/02 1:50 PM Page 12