high oil pressure - 70 at cruise ('89 454)

My port oil pressure gauge reads around 45-50 but the needle bounces all over the place. I cleaned connections on both ends and assume it's a flaky pressure sending unit.

The Starboard side reads around 60 (steady) and has since I bought the boat last year. I noticed it's closer to 70 lately at cruise, it maxes it out at 80.

Assuming that gauge is accurate (big IF), what are the typical causes of high pressure? Engine starts, runs and sounds just like my port side.

It's always started out higher than the other side but this bump up is a new development.

Bob

Flaky sending units are pretty common, especially when they age. I'd put a mechanical gauge on first and see if what the gauge is showing represents reality.

Do you know the history on the engines....any reason to think the oil pump(s) have been changed?

Mark, I don't think any bottom work was ever done, possibly a valve job or at least the intake manifold was off at some point. High volume oil pump? I would say highly unlikely.

Since the other one is bouncing around, I just ordered two new sending units. I'll swap them both and see what changes. If still high, I'll check with a mechanical gauge. I searched around and 70-80 doesn't seem to be crazy high at least to some people.

I'll post back, I should have them in a couple of days. I still have my brand new u-coolers on board to install. Both engines run 170 at cruise so this is purely preventative.

THEN, I'm done

Yep, very likely instrumentation error. Good thing too, that oil relief system (spring and a plate) is just about the MOST difficult piece of the engine to get to in a boat.

You said it! It's good practice to always check oil pressures with a mechanical gage before believing what those lying instruments tell us.

Jeff

High (or what I call excessive oil pressure), contrary to what some may think, is not necessarily a good thing!
It is unlikely that the oil pump is actually producing 80 psi. While capable of greater pressure, the pressure relief valve in the GM pump controls this.

I too would think that you have a sending unit or instrument issue.

Note that a Dual Helm scenario requires a different sending unit from that of a single station.

I have a new sending unit on my desk and will install tonight.

Ricardo - I just sent you a PM, a friend of mine is looking at a boat with a Volvo Penta 5.7 (2000, raw water cooled) engine and wanted to get your general opinion.