Losing Oil Pressure?

[NickOTeen]

I’m having an issue with my starboard side motor losing oil pressure, and I’m looking for a diagnosis from the resident experts. Here are the symptoms.

At the beginning of the summer the starboard side motor would start losing oil pressure after 15-20 minutes of running time. We thought it was a gage problem so I replaced the sending unit as well as changed the oil. After that everything was fine. Fast forward to now.

The oil has 25 hours on it and I’m seeing the same drop in pressure that I was seeing at the beginning of the summer. Hoping it might be the sending unit again we put a mechanical gage on the motor, but experienced the same pressure drop. Both motors generally run between 45-60 PSI depending on how hard I’ve been running. Now after 15 minutes of running time the starboard side oil pressure will completely fall off from 50 PSI to just under 20 PSI. It’s not a gradual decrease either it just drops. Now if I let the boat sit for 10 minutes and fire it back up the pressure will go back to normal for another 5 minutes or so. The oil temp for the starboard side is now consistently 25 to 30 degrees higher then the port side. I’m currently running twin 350s with Prochargers. I’m using Valvoline 50 weight oil. Any thoughts?? I don’t run the boat hard, and I can’t imagine the oil breaking down after just 25 hours? I plan on pulling the motor this winter. Where should I start? Thanks.

NickOTeen

[PatriYacht]

What are your oil temps after a hard run?

[1BIGJIM]

I had the exact same problem last year.
Simple cheap test,
Cut open your oil filter and check for little shiny pieces of copper bearing material.

[NickOTeen]

What are your oil temps after a hard run?

180-190 normally. Starboard will run up to 220 now. Of course I cut the motors when the pressure drops.

There is no metal in my oil filters whatsoever. Both engines still purr like kittens.

[PatriYacht]

If your temps are that low and you can't hold good oil pressure with 50 weight oil, you're goinig to have to pull the engine to investigate. How many hours on the engine?

[NickOTeen]

If your temps are that low and you can't hold good oil pressure with 50 weight oil, you're goinig to have to pull the engine to investigate. How many hours on the engine?

250. Probably won't pull the motor until later this winter. It will be interesting to see what we find.