TROUBLESHOOTING - 1C- 23
90-816462 2-695
Engine Noise
Important Information
No definite rule or test will positively determine
source of engine noise; therefore, use the following
information only as a general guide to engine noise
diagnosis.
1. Use a timing light to determine if noise is timed
with engine speed or one-half engine speed.
Noises timed with engine speed are related to
crankshaft, rods, pistons, piston pins, and fly-
wheel. Noises timed to one-half engine speed are
valve train related.
2. The use of a stethoscope can aid in locating a
noise source; however, because noise will travel
to other metal parts not involved in the problem,
caution must be exercised.
3. If you believe noise is confined to one particular
cylinder, ground spark plug leads, one at a time.
If noise lessens noticeably or disappears, it is iso-
lated to that particular cylinder.
4. Try to isolate the noise to location in engine: front
to back, top to bottom. This can help determine
which components are at fault.
5. Sometimes noises can be caused by moving
parts coming in contact with other components.
Examples are: flywheel or coupler; exhaust flap-
pers rattling against exhaust pipe; crankshaft
striking (pan, pan baffle, or dipstick tube); rocker
arm striking valve cover; and loose flywheel cov-
er. In many cases if this is found to be the problem,
a complete engine teardown is not necessary.
6. When noise is isolated to a certain area and com-
ponent, removal and inspection will be required.
Refer to proper sections of service manual for in-
formation required for service.
7. If noise cannot be distinguished between engine
and drive unit, remove drive from boat. Run a wa-
ter supply directly to engine. Run engine without
the drive to determine if noise is still there.
Valve Cover Area
Location
Possible Cause
1. Valve cover area, timed to one-half engine
speed, noise could be confined to one cylinder
or may be found in any multitude of cylinders
1. A. Rocker arm striking valve cover
B. Rocker arm out of adjustment
C. Worn rocker arm
D. Bent push rod
E. Collapsed filter
Cylinder Area
Location
Possible Causes
1. Cylinder area, may be confined to one cylinder
or found in more than one cylinder, timed to
engine speed
1. A. Sticking valve
B. Carbon build-up
C. Connecting rod installed wrong
D. Bent connecting rod
E. Piston
F. Piston rings
G. Piston pin
H. Cylinder worn
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Страница 1: ...13 Printed in U S A 90 816462 2 695 1995 Brunswick Corporation GM 4 Cylinder MARINE ENGINES ...
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Страница 7: ...1 A IMPORTANT INFORMATION GENERAL INFORMATION 72000 ...
Страница 15: ...1 B 50617 IMPORTANT INFORMATION MAINTENANCE ...
Страница 36: ...1 C IMPORTANT INFORMATION TROUBLESHOOTING ...
Страница 74: ...2 A 50633 REMOVAL AND INSTALLATION 4 CYL ALPHA ONE DRIVE ...
Страница 88: ...3 A 26790 ENGINE 181 CID 3 0L 4 CYLINDER GM ENGINE ...
Страница 137: ...4 A 72079 ELECTRICAL SYSTEMS STARTING SYSTEM ...
Страница 170: ...4 B 71855 ELECTRICAL SYSTEMS IGNITION SYSTEM ...
Страница 197: ...ELECTRICAL SYSTEMS CHARGING SYSTEM 4 C 72078 ...
Страница 237: ...4 D 72747 ELECTRICAL SYSTEMS INSTRUMENTATION ...
Страница 250: ...4 E 72938 ELECTRICAL SYSTEMS WIRING DIAGRAMS ...
Страница 264: ...5 A FUEL SYSTEM FUEL PUMP ...
Страница 271: ...5 B 72681 FUEL SYSTEM MERCARB 2 BARREL CARBURETOR ...
Страница 300: ...6 A 50628 COOLING SYSTEM SEAWATER COOLED MODELS ...
Страница 309: ...6 B 73665 COOLING SYSTEM CLOSED COOLING MODELS ...
Страница 325: ...C 6 EXHAUST SYSTEM MANIFOLD ...
Страница 331: ...7 A 71317 POWER STEERING PUMP ...