oil pressure question (pretty high)

[boatman37]

So had the boat out yesterday and today and noticed pretty high oil pressure. We just bought the boat last August but the boat was docked across from us in 2015. Only ran it a few times last season and never noticed it but noticed yesterday and today that it was running around 70-80 PSI while running about 3500-4000 RPM. It isn't pegged just high. I know all about the 10 PSI per 1000 RPM and all that. But sitting here tonight remembered back in 2015 the previous owner asking a dock neighbor about their gauge being pegged. He told her the sending unit was bad. At times today it would drop to about 55-60 then back up. I'm guessing I either have a bad gauge or sending unit? It is a 2006 Crownline 250CR with a 5.7 Merc and Faria gauges.

Might go pick up a mechanical gauge and test it for verification but may just replace the sending unit first to eliminate that. Are these Merc specific or any small block chevy sending unit work?

 

[alldodge]

Could be gauge, sender or chafing on the wire. For it bouncing I would first think its the gauge and some corrosion, but could still be the sender. A mechanical gauge would verify

 

[boatman37]

Not really bouncing. Most of the time it stays between 70-80 PSI but then might drop to 50. Not really a quick bounce. More like a real slow bounce...lol

 

[aerobat]

my 5.0 mpi idles at about 45psi und goes at WOT also to 75 or so. maybe its the nature of the beast ?

my carbed 3.0 was far lower regarding oil pressure

 

[alldodge]

Its very unusual to see oil pressure above 60 psi or so in a stock build. My thought is its just the gauge/sender

 

[boatman37]

I will look into swapping the sending unit and checking it with a manual gauge for verification

 

[Scott06]

I had a similar situation where at sustained high speed runs oil pressure would drop like you are seeing. Replaced sender same thing, hooked up a mechanical guage and get same as dash guage... found I was over filling the oil by about a quart and I think I may have been foaming the oil at higher sustained rpms as pressure would come back up if I stopped for ten minutes. Pullled half a quart out and issue went away.

Just a thought given similarty in pressures you and I were seeing.

 

[boatman37]

I checked everything after our first time out Saturday and oil level looked good but it was a little hard to tell exactly where it was on the dipstick. I changed the oil before winter and it is still really clean so hard to see. Will check it again this weekend

 

[QBhoy]

It defo shouldn’t be this high.
Mine once warmed up will be just over 40 at low rpm and no more than 50 something higher rpm. Always suspect gauges, but if it’s genuinely that high, I’d be looking at the temperature next time out. You may have a stuck open t stat ?

 

[boatman37]

Temp was good. Right around 170 or just slightly over that. Impeller and housing were replaced last August when I bought it

 

[Boater31]

I got a 99 4.3 vortec and after being warmed up at pretty much anything other then idle I'm 65 to 75 psi. Idle is about 40 to 45. It's been this way since I owned it. Oil is 3/4 on dipstick in water.

 

[Scott Danforth]

verify the oil pressure with a mechanical gauge

it could be the $3 sender or the $3 gauge that is put in boats.