I am having problem with my oil pressure dropping. I lost a motor about 3 months ago. I rebuilt the motor and put it back in the boat. I ran it for about a month and when i would power down from about a 15 min. run. My oil pressure would drop to about 10 lbs. I could crank the motor back and the pressure would still be low. If i powered back up the pressure would return to 50lbs. I changed the oil filter and that seamed to fix the problem. I figured that i might still have some trash in the oil cooler that i couldnt get out. This weekend the same thing happened. I changed the filter but it is still low pressure when i am idling. Can anyone give me some insight on my problem......Thanks

Does the pressure go back up on cold start? Does the oil cooler warm up when the engine is warm? Sounds like hot oil may be a problem.

The pressure is good when it is cold also. The temp is the same as the other motor also.

Try the easy stuff first by switching the oil senders from one to the other.

I had a similar problem years back with a big block Ford. After pulling most of my hair out , I found my "reconditioned" rods weren't recond properly. Top to bottom across the bearing was fine , but go side to side and I had .005 to .006 clearance. As soon as it got up to operating temp , I had 5 lbs at idle. Running still gave me 45 or so. Redid the rods and 70 lbs cold , 60 hot , 45 idle.
I'm sure this is NOT what you want to hear.

Classic signs of engine problem.

Could be the wrong spring in the oil pump giving you low pressure at idle once the motors is hot.

What weight oil do you run?