1999 Mercruiser HI-Performance GM 377 EFI Engine Service Manual, Page 50Get this manual

1999 Mercruiser HI-Performance GM 377 EFI Engine Service Manual, Page 50

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TROUBLESHOOTING
Mechanical Damage
Mechanical damage to spark plug firing end is caused by foreign object in combustion chamberBecause of valve overlap, small objects can travel from one cy