SERVICE MANUAL NUMBER 25
TROUBLESHOOTING
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 flywheel. Noises timed to one-half engine speed are valve train related.
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 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 isolated to that particular
cylinder.
4.
5.
Try to isolate the noise to location in engine: front to back, top to bottom. This can help
determine which components are at fault.
Sometimes noises can be caused by moving parts coming in contact with other
components. Examples are: flywheel or coupler; exhaust flappers rattling against
exhaust pipe; crankshaft striking (pan, pan baffle, or dipstick tube); rocker arm striking
valve cover; and loose flywheel cover. In many cases if this is found to be the problem,
a complete engine teardown is not necessary.
6.
7.
When noise is isolated to a certain area and component, removal and inspection will be
required. Refer to proper sections of service manual for information required for service.
If noise cannot be distinguished between engine and drive unit, remove drive from boat.
Run a water supply directly to engine. Run engine without the drive to determine if noise
is still there.
Valve Cover Area
Location
Possible Causes
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 lifter
90-861328--1
NOVEMBER 1999
Page 1C-17
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 1262 CID, Mercury MerCruiser 262 CID |
| Model Year | 1998, 1999, 2000, 2001 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
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