MerCruiser 13, Service Manual

Page: 64 / 348

TROUBLESHOOTING - 1C- 27 90-816462 2-695
Oil Pressure
1. Measuring oil pressure 1. Use a good automotive oil pressure test gauge.
Do not rely on the oil pressure gauge in the boat.
2. Check engine oil level with boat at rest in the
water
2. Oil level should be between the ADD and FULL
marks
3. Oil level in crankcase above FULL mark 3. May cause loss of engine RPM, oil pressure
gauge fluctuation, drop in oil pressure, and hy-
draulic valve lifter noise at high RPM
4. Oil level in crankcase below ADD mark 4. Low oil pressure; oil pressure gauge fluctuation;
internal engine noise and/or damage
5. Change in oil pressure 5. 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.
6. Low engine oil pressure at idle 6. 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 lubri-
cate 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 thinout
somewhat from heat.
7. Low engine oil pressure at idle after running at a
high RPM
7. Refer to No. 5 and 6, preceding
8. Boats with dual engines 8. It is not uncommon to see different oil pressure
readings between the two engines, as long as
both engines fall within specifications. Differences
in oil pressure can be attributed to differences in
engine tolerances, gauges, wiring, senders, etc.
9. Boats with dual stations 9. Refer to No. 8. preceding