2.5l mercruiser - high oil pressure, oil leaks

Hello All, Well here is the deal. I put in a rebuilt 2.5l mercruiser into my boat last fall. This spring have been working out the kinks... rebuilding the carb, grease, lube, impeller, etc. running in the driveway on muffs, the oil pressure has been high maybe 70psi ish. Oil was just driping a little from the seal on the starboard side of the motor and a little around the valve cover.

Well... move the boat to the water and run with a little highr RPM and under load and the dripping and turned to a steady trickle, the oil PSI is up to about 80 at 3000 rpm.

From my research, I believe that I have a problem with the pressure relief valve or spring... I believe it is located in the oil pump. I believe that I need to pull the motor to correct this.

Any help, or thoughts would be greatly appreciated. Things to try before the motor gets pulled? is it possible to get at this without pulling the motor? Other experiences?

Thank you in advance.

Re: 2.5l mercruiser - high oil pressure, oil leaks

What kind of gauge (and brand) are you using to confirm your oil pressure?

80 psi isn't all that high.

Oil pressure and the oil seals doing their job are 2 different things.

Re: 2.5l mercruiser - high oil pressure, oil leaks

Well thank you or the quick reply. I am measuring oil pressure on the dash gage, have not confirmed mechanically. I assumed it was accurate because of the oil leaks and 80 PSI seamed very high to me. Is 80 PSI reasonable to run at, and can gaskets be expected to hold up at 80 PSI if that is indead accurate?

thank you so much again for your input.

Re: 2.5l mercruiser - high oil pressure, oil leaks

80 psi is fine, its a sign of a healthy oil pump and a tight bottom end.

Oil pressure and oil leaks are 2 different things. Oil seals on an engine don't hold pressure in, as the crankcase is vented to atmosphere. And there is no direct oil pressure against any seal.

I think you just have a leak my friend.

Re: 2.5l mercruiser - high oil pressure, oil leaks

Well, thank you again. Much happier to to get a couple of new gaslets to install than contemplating getting at a pressure regulator in an oil pump underneath the engine.

Any recommendations on very good gaskets?

Re: 2.5l mercruiser - high oil pressure, oil leaks

OEM only on anything rubber.

Re: 2.5l mercruiser - high oil pressure, oil leaks

thank you again for your help. I thought it only fitting to reply after implementing the adivice I received. I replaced both the valve cover gasket and the push rod cover gasket. No leaks whatsoever of oil anymore and pressure still running in the 70 range which i feel a lot better about without oil leaks.

When taking the valve cover off to get at the gasket, I realized the biggest problem was that on the left side of the valve cover seal surface on the head, there are only two bolts and about 6 or 7 inches of surface between them. the surface the gasket sit on is maybe a 1/4 in wide ridge running between the two bolts, the old gasket, when previously installed had kind of pushed in a little bit and wasn't seted between the two surfaces. It is an easy error to make, having seen the old one, knowing what I was trying to avoid, I still had to take a few tries at it to get the gasket to seat properly. Anyway, with the old gasket pushed in, it left a small gap completly open between the valve cover and the head. The oil was just running out of this gap.

Note to myself and others.... check all of the obvious things before moving on to the more complex when trying to diagnose and solve a problem.