Inspecting Spark Plug - Yamaha F150D Owner's Manual

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Inspecting spark plug

The spark plug is an important engine com-
ponent. The condition of the spark plug can
indicate something about the condition of the
engine. For example, 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 out-
board motor to a Yamaha dealer. You should
periodically remove and check the spark plug
because heat and deposits will cause the
spark plug to slowly break down and erode.
To remove the spark plug
1. Remove the cover.
1. Cover
2. Remove the spark plug cap from the
spark plug.
1. Spark plug cap
3. Remove the spark plug. WARNING!
When removing or installing a spark
plug, be careful not to damage the in-
sulator. A damaged insulator could al-
low external sparks, which could lead
to explosion or fire.
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To check the spark plug
1. Check the condition of the spark plug. If
electrode erosion becomes excessive or
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carbon and other deposits are exces-
sive, replace the spark plug with the
specified plug.
Standard spark plug:
LFR5A-11
2. Measure the spark plug gap using a
thickness gauge. If the spark plug gap is
out of specification, replace the spark
plug with the specified plug.
Maintenance
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