1C- 2 - TROUBLESHOOTING
90-816462 2-695
Used Spark Plug Analysis
Use the following illustrations for determining ser-
viceability of spark plug. Spark plug condition also
can suggest a variety of possible engine malfunc-
tions and, therefore, can indicate needed engine
repairs. When old plugs are replaced, replace en-
tire set. Perform plug service only on those plugs
suitable for additional service, using the following
procedures:
1. Remove any oil deposits with solvent and dry
plugs thoroughly.
2. Open electrode gap wide enough to permit clean-
ing and filing.
3. Remove combustion deposits from firing end of
spark plug with a plug cleaner. Blow off with com-
pressed air to remove abrasives.
4. File electrode surfaces to restore clean, sharp
edges. Again remove filings with compressed air.
5. Reset gap to specifications by bending only side
electrode with proper tool.
IMPORTANT: When working on engine, spark
plug holes and carburetor throat should be kept
covered to prevent foreign objects from entering
combustion chamber.
Spark Plug Analysis
Normal Condition
Few deposits are present and probably will be light
tan or gray in color. This plug shows that plug heat
range is compatible with engine, and engine is
electrically and mechanically in good running condi-
tion. With proper plug servicing (clean, file and re-
gap), this plug can be reinstalled with good results.
72420
Chipped Insulator
Chipped insulator usually results from careless plug
re-gapping. Under certain conditions, severe deto-
nation also can split insulator firing ends. Plug must
be replaced.
72420
Wet Fouling (Oil Deposits)
Plug becomes shorted by excessive oil entering
combustion chamber, usually in engine with many
hours of operation. Worn piston rings, cylinder
walls, valve guides or valve stem seals are causes
of oil entering combustion chamber. Only engine
repairs will permanently relieve oil wet fouling.
IMPORTANT: New engines or recently overhauled
engines may wet foul plugs before normal oil con-
trol is achieved with proper break-in procedures.
Such fouled plugs may be serviced (clean, file
and re-gap) and reinstalled.
72420
Summary of Contents for 13
Page 1: ...13 Printed in U S A 90 816462 2 695 1995 Brunswick Corporation GM 4 Cylinder MARINE ENGINES ...
Page 2: ...90 816462 2 695 0 ...
Page 7: ...1 A IMPORTANT INFORMATION GENERAL INFORMATION 72000 ...
Page 15: ...1 B 50617 IMPORTANT INFORMATION MAINTENANCE ...
Page 36: ...1 C IMPORTANT INFORMATION TROUBLESHOOTING ...
Page 74: ...2 A 50633 REMOVAL AND INSTALLATION 4 CYL ALPHA ONE DRIVE ...
Page 88: ...3 A 26790 ENGINE 181 CID 3 0L 4 CYLINDER GM ENGINE ...
Page 137: ...4 A 72079 ELECTRICAL SYSTEMS STARTING SYSTEM ...
Page 170: ...4 B 71855 ELECTRICAL SYSTEMS IGNITION SYSTEM ...
Page 197: ...ELECTRICAL SYSTEMS CHARGING SYSTEM 4 C 72078 ...
Page 237: ...4 D 72747 ELECTRICAL SYSTEMS INSTRUMENTATION ...
Page 250: ...4 E 72938 ELECTRICAL SYSTEMS WIRING DIAGRAMS ...
Page 264: ...5 A FUEL SYSTEM FUEL PUMP ...
Page 271: ...5 B 72681 FUEL SYSTEM MERCARB 2 BARREL CARBURETOR ...
Page 300: ...6 A 50628 COOLING SYSTEM SEAWATER COOLED MODELS ...
Page 309: ...6 B 73665 COOLING SYSTEM CLOSED COOLING MODELS ...
Page 325: ...C 6 EXHAUST SYSTEM MANIFOLD ...
Page 331: ...7 A 71317 POWER STEERING PUMP ...