Hostile Takeover

I am running a 454 HO Carb motor w/oil cooler. when I am warmed up at idle the oil pressure reads approx 10 psi. However when I make a high speed run and throttle down to idle the pressure drops to almost nothing. I can bring it up by shifting into forward and bringing the rpms up to about 1000 or keeping the boat in neutral and throttle up to 1000 rpm. Does this indicate I have a big problem?

HiPerf2000

how many hours on the motor? What are the numbers cold?

I would put a mechanical guage on it and see what it's really doing.

Hostile Takeover

300 hrs. Oil pressure is good even when cold. It only drops after a high speed runs.

formula31

Like hiperf said, verify with a mechancal gauge. What oil are you using? Hot oil pressure is always lower than cold and you should have an oil temp gauge to find out how hot your oil is getting. If its over 250 you might want to consider a bigger oil cooler or try synthetic which I hear handles higher temps better.

PatriYacht

Does not sound good, however I have a Merc 350 Magnun in a ski boat that has done that since new. 400 hrs and 9 years later still run great. In a high performance application, I would not be comfortable with pressure being that low. What oil do you use?

Edward R. Cozzi

You never mentioned the warning buzzer. I had a bad sender once. I had plenty of OP, and the buzzer never sounded.

Food for thought:
Saw a Ford engine once that did the same thing. The oil return galleries were clogged and the oil got trapped high in the engine after a while. Took several minutes for it to drain back to the pan where the oil pump could get it again.

Saw an engine do this that had excessive bearing clearances too.

jpclear

An old basic rule of thumb: OP should NEVER be below 10#/1000 rpm at any temp. --- JP

offthefront

Wonder if it was clogged galleries if you could run a quart of MMO and help clear things out ?