Engine Noise
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.
Important Information
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 prob-
lem, a complete engine teardown is not neces-
sary.
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.
6.
7.
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.
2.
3.
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.
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.
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.
Valve Cover Area
Location
Possible Cause
Rocker arm striking valve cover
Rocker arm out of adjustment
Worn rocker arm
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
Bent push rod
Collapsed filter
Index
1C-18 - TROUBLESHOOTING
90-823224--2 796
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 454 CID, Mercury MerCruiser 502 CID |
| Model Year | 1993, 1994, 1995, 1996, 1997 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
(4 votes, average: 4.5 out of 5)
Marine readers have rated 1993 1997 Mercury-MerCruiser GM V8 454 CID 7.4L and 502 CID 8.2L Marine Engines Service Manual Number 16 4.5 out of 5.0 based on 4 product reviews. Hugely helpful service manual! Perfect. Thank you!
Manuals are all Important for Technician
This book is invaluable if you do your own repairs. Great book.
Could not find a copy until a search brought me here.
Excellent print.
Thank you