I have a twin engines that are 500EFI rebuilt last winter. Both oil pump housings and gears looked great after pulling the covers, so I reused them. Oil coolers and all other coolers where rodded and cleaned on both motors.
Have put about 15 hrs of various driving on both engines and they seem to run great. During the first 3-4 minutes running, both motors maintain 60+ psi. Then the starboard motor will drop down to 38-40 psi while the other stays at 50psi. Come down off plane to idle and the starboard drops to 25 psi and the other 40 psi. Idle around for 5 minutes and the lower one comes back up to 50psi. I'm worried that 38psi might not be suficient pressure for 5300 rpm.

This lower oil pressure is driving me crazy. Can anyone shed their thoughts on this? Thank you!


Engine water temp= 155*
Engine oil temp = 170*
Mobil 1 15w-50 oil
FLORIDA air temps

Check the sending units make sure there OK.

What pump are you using?