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

SERVICE MANUAL NUMBER 23

Oil Pressure

Miscellaneous

Measuring oil pressure
Check engine oil level with boat at rest in
the water
Oil level in crankcase above FULL mark
Oil level in crankcase below ADD mark
Change in oil pressure
Low engine oil pressure at idle
Low engine oil pressure at idle after run-
ning at a high rpm
Boats with dual engines
Boats with dual stations
Index Index
90-861326--1 MARCH 1999
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Cause Special Information
Use a good automotive oil pressure test
gauge. Do not rely on the oil pressure
gauge in the boat.
Oil level should be between the ADD and
FULL marks
May cause loss of engine rpm, oil pres-
sure gauge fluctuation, drop in oil pres-
sure, and hydraulic valve lifter noise at
high rpm
Low oil pressure; oil pressure gauge
fluctuation; internal engine noise and/or
damage
This may be a normal condition. Oil
pressure may read high in the cooler times
of the day, and when engine is not up to
operating temperature. As the air
temperature warms up and engine is
running at normal opening temperature, it
is normal for oil pressure to drop.
With modern engines and engine oils, low
oil pressure readings at idle do not
necessarily mean there is a problem. If
valve lifters do not "clatter" (at idle), there
is a sufficient volume of oil to lubricate all
internal moving parts properly. The reason
for the drop in oil pressure is that engine
heat causes an expansion of the internal
tolerances in the engine and, also, the oil
will get thin somewhat from heat.
Refer to the two preceding steps
It is not uncommon to see different oil
pressure readings between the two
engines, as long as both engines fall
within s ecifications. Differences in oil within specifications Differences in oil
pressure can be attributed to differences
in engine tolerances, gauges, wiring,
senders, etc.
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