Low Oil Pressure; High Oil Pressure - Mercury MerCruiser MCM 454 Mag MPI Service Manual

TROUBLESHOOTING

Low Oil Pressure

Low oil level in crankcase
Defective oil pressure gauge and/or
sender
Thin or diluted oil
Oil pump
Oil leak can be internal or external
Excessive bearing clearance

High Oil Pressure

Oil too thick
Defective oil pressure gauge and/or
sender
Clogged or restricted oil passage
Oil pump relief valve stuck closed
Index Index
Page 1C-20
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Cause
Cause
SERVICE MANUAL NUMBER 23
Special Information
Verify with an automotive test gauge.
Refer to SECTION 4D for instrument
testing.
Oil broken down; contains water or gas;
wrong viscosity; engine running too hot or
too cold; excessive idling in cold water
(condensation)
Relief valve stuck open; pickup tube
restricted; worn parts in oil pump; air leak
on suction side of oil pump or pickup oil
tube
Oil passage plugs leaking, cracked or
porous cylinder block
Cam bearings, main bearings, rod
bearings
Special Information
Wrong viscosity, oil full of sludge or tar
Verify with an automotive test gauge
90-861326--1 MARCH 1999