SERVICE MANUAL NUMBER 24
TROUBLESHOOTING
Reversed Coil Polarity
Concave erosion of ground electrode is an indication of reversed polarity. Center electrode
will show only normal wear. Engine will misfire and idle rough. To correct, reverse primary
coil leads. Replace spark plugs.
72422
Splashed Deposits
Spotted deposits, which sometimes occur after long delayed tune-up, accumulate after a
long period of misfiring. When normal combustion temperatures are restored, upon installa-
tion of new plugs, deposits loosen from top of piston and head and are thrown against hot
insulator. Plugs can be serviced (clean, file and regap) and reinstalled.
72423
Mechanical Damage
Mechanical damage to spark plug firing end is caused by foreign object in combustion
chamber. Because of valve overlap, small objects can travel from one cylinder to another.
Check all cylinders, intake manifold and exhaust material to prevent further damage.
Replace spark plugs.
72423
IMPORTANT: When working on engine, spark plug holes, carburetor throat and
throttle body should be kept covered to prevent foreign objects from entering com-
bustion chamber.
Index
90-861327--1
OCTOBER 1999
Page 1C-5
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 305 CID, Mercury MerCruiser 350 CID |
| Model Year | 1998, 1999, 2000, 2001 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
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Marine readers have rated Mercury MerCruiser Engines Service Manual Number 24 GM V-8 305 CID 350 CID 4.0 out of 4.0 based on 1 product reviews. Great performance engine.
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