Oil pressure question........AGAIN !!!!!
 

I am still having oil pressure issues. I have a pair of 540's that I have totally gone through after melting one down last year. The first time I had her out this year, the port engine would lose oil pressure at about 4500 RPM. The oil held at about 55 psi until you run over 4500, then drop to about 30psi. The starboard engine held steady at 60psi throught the RPM range. Last weekend both engines started doing the same thing. 55-60 psi until about 4500 RPM, then drop to 25 - 30 and hold steady. If I back off the throttles both will jump right back up to 55-60. I double checked the oil level. Oil is clean and full. Oil temps are about 230, so it isn't temp related. I am beginning to wonder if the trap doors on my Dooley pans are stuck. Could it be something in the oil filter or cooler ??
I ran it hard for about 10 miles, and it didn't seem to bother it, but it bothers me. Any one have any suggestions ?

Dumb question here but...... Did you check the pickup height on the port motor before you buttoned the pan up? did the motor have this problem on the dyno if you dyno'd it?

I have a motor that does the exact same thing. I'm also running 540's. It's almost like it runs out of oil at high rmps. Back off for a while and pressure creeps back up. I was hoping to get through the summer than get it tore down. I run rotella 15-40 for oil what about you.

Mr3dman- Not a dumb question, yes, I set the pick up depth to about 1/2" off the bottom. The engines were not dyno'd this time around.

jbraun2828 - I am running straight 30 penzoil. I am also on you plan, hope to make it through the summer, then take them apart AGAIN !!!!

The pans are 10 qt, so it shouldn't ever run out of oil, but that is what it seems like. It did not have this issue last year before the one blew. I had them both apart over the winter, figuring as long as I am taking one apart, I would re-ring and bearing the "good" one to make sure.

Have you tried running 9 qts in your 10qt pan? Sometimes the oil will froth/aerate in higher RPM. I would think if you were sucking the pickup dry, you'd see major fluctuations on the gauge, and probably do some damage in a short time.

Worth a try
 

Not a bad thought. It's worth a try. I was thinking the same thing on the damage, if it was drying up I would suspect damage by now.

You need to validate with a mechanical gage. Sending units can cause that sympton. Also when installing, you shouldn't use pipe sealer on the sending unit threads. It grounds through those threads. I had one of my new mills this yr doing exactly what you say and with a mech gage I had 70psi when the gage was saying 30. Let up on the throttle and the electric gage would go back up. New sending unit with no sealer now and my electric gage matches what the mech was reading. I would also switch to a 15-50ish synthetic oil if I were you.

I agree here too. When I bought my new 10qt pans a few yrs back before I assemble the engines I dumped 10qts in the pan and quickly realized that was too much. 8 qts is what they can hold without being over full with a potential for windage. You can usually tell if you have windage issues because there will be a burnt oil smell in your engine room from oil splashing up on the underside of the pistons.

I don,t think the engine is running out of oil ,I would think if it did ,the oil pressure would be zero to almost nothing , the oil pump is going to suck air if the oil pan is sucked ''dry'' and hydraulic pressure would be almost gone .
Could it be the springs in the oil pumps that are too weak ?
Or worser ,crankshaft /con rod /mains play to big ?
You have to find this problem ,this is no good

Blue Thunder - I knew better than to use sealer on the pressure sender threads, but did it without thinking. I figured that it may cause an in accurate reading, but am surprized by the changing pressure reading. I'll hook up a mech gauge this weekend.