Spark Plug Inspection And Replacement - Mercury 150 Operation, Maintenance And Installation Manual

9. Secure the propeller nut by bending three of the tabs into the thrust hub
grooves.

Spark Plug Inspection and Replacement

Damaged spark plug boots may emit sparks that can ignite fuel vapors under
the engine cowl, resulting in serious injury or death from a fire or explosion.
To avoid damaging the spark plug boots, do not use any sharp object or
metal tool to remove the spark plug boots.
1. Remove the spark plug leads by twisting the rubber boots while pulling
them off the spark plugs.
2. Remove the spark plugs. Replace the spark plug if the electrode is worn;
the insulator is rough, cracked, broken, or blistered; or if the precious
metal is not visible on the spark plug electrode.
MAINTENANCE
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