Merc 5.7 oil pressure is unusually high

[jumpjets]

I just did my own oil change. Over the past two years, the shop that winterized my boat has done an oil change for me as part of the winterization service. I do not know what type of oil they used.

I put synthetic 10W-30 in the engine when I did the oil change. Now the oil pressure is pretty high. It it used to idle at 15-20 psi, and now it idles at 35-40 psi. At 2000rpm, it has 50-55 psi. It used to have 35-30psi. At wide open, it has 60+ psi. It used to 45 psi.

This is a pretty old engine. Additionally, gen I chevy small blocks usually have pretty low oil pressure. This seems like it might be too high. Am I at risk of damaging anything? Should I change the oil to something else?

 

[Bt Doctur]

Re: Merc 5.7 oil pressure is unusually high

10-30`s a bit thin, 25W-40 or 20W-50 would be better. temporarily install a gauge to verify the sender readings. might have a sender going bad.

 

[Lager]

Re: Merc 5.7 oil pressure is unusually high

The boat doctor is correct, your 10-30 is a bit thin for a small block chev engine.
Concerning your pressure, it does appear to be a bit high, your original reads were probably correct.
Might have a sender or a gauge reading incorrectly, up to you if you really want to figure out the cause.
Excessive oil pressure can be a problem and is usually caused by a stuck closed oil pressure relief valve mounted on your oil pump and inside the engine.But, that's not the problem because high oil pressure happens at high rpm, not at idle.
Hope this helps

 

[Bondo]

Re: Merc 5.7 oil pressure is unusually high

Ayuh,.... Fresh oil in a cold motor ain't much of a Test,.....

 

[jumpjets]

Re: Merc 5.7 oil pressure is unusually high

I ran it for a solid two hours on the river today. At first it was 2500rpm and 60psi on the gauge. After ~30min of run time, the pressure dropped slowly to 40psi. I'll install an aux gauge. I'd believe that the gauge might be going bad.