TROUBLESHOOTING
SERVICE MANUAL NUMBER 25
Engine Overheats
Mechanical
Cause
Special Information
Engine rpm below specifications at wide-
open-throttle (engine laboring)
Damaged or wrong propeller; growth on
boat bottom; false bottom full of water
Wrong ignition timing
Timing too far advanced or retarded
Sticking distributor advance weights
Spark plug wires crossed (wrong firing
order)
Lean fuel mixture
Wrong heat range spark plugs
Exhaust restriction
Jumped timing chain, or improperly
installed
Valve timing off
A blown head gasket(s) normally cannot
be detected by a compression check. Nor-
mally the engine will run at normal temper-
ature at low rpm, but will overheat at
speeds above 3000 rpm.
Engines that are seawater cooled:
Using a clear plastic hose, look for air
bubbles between seawater pump and
engine. If there are no bubbles present,
install clear plastic hose between
thermostat housing and manifold(s). If air
bubbles are present at a higher rpm, it is a
good indication there is a blown head
gasket.
Blown head gasket(s)
Insufficient lubrication to moving parts of
engine
Defective oil pump, plugged oil passage,
low oil level
Page 1C-26
90-861328--1 NOVEMBER 1999
| 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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