You did not really tell us what you consider "low". The 10lbs per
1,000 rpm is a good measure. Many oil pumps have a pressure relief
valve that will keep the pressure from going above something between 45
and 80lbs depending on the spring in the relief valve. The goal is not
to get the maximum pressure but to get the appropriate oil flow for the
engine.

The drain back holes in the heads and lifter valley are pretty big so I
doubt that they are clogged. (It's actually a racing trick to block a
number of those off to reduce the oil dropping on the crank. Forcing
the oil to the rear drain holes.) I agree too about the amount of oil.
Change it and after putting in the recomended amount, probably 5
quarts, run it a little, and then take a look at the dipstick with the
boat level on the trailer. See if it is close to the mark. If it's
not make a new mark on the dipstick.

There are other possibilities like a missing windage tray or the pickup
has fallen or broken off the oil pump. To check these requires
removing the engine so you need to eliminate everything else. Other
things that release a lot of oil like plugs falling out of oil journals
can also cause low pressure but that would be all the time.

You should not run the engine under a load for any length of time at
all with dangerously low oil pressure. I'd say anything under 20lbs
while under load is a big concern. Very low oil pressure will wear out
things really fast. If the oil gauge is intermittently dropping to
zero due to oil starvation at the pump you need to fix it now. That
will ruin your engine.

JR North wrote:
Drain whatever multi-grade oil the previous idiot put in and refill
w/straight HD 30wt. Report back.
JR

wrote:

I just bought a 18' Bryant BB180. The engine is a 4.3 mercruiser, the
boat is in perfect condition and it runs awesome. Once I take off and
get up on plane and get the trim up, my oil pressure wants to run low.
A mechanic told me that the motor is sucking up all the oil, and not
leaving any in the oil pan, resulting with low oil pressure. If you
have any idea on how to fix my problem, please respond or send me an
email. Thanks alot.



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