Recently my Merc 5.7 was rebuilt and there seems to be a high oil presure reading on the guage +95psi at idle. A high volume oil pump was installed at rebuld time. I changed the guage out and it still is "pinned", I'm using 25/40 oil, any ideas?
dont know but thats way to much pressure if the sender is accurate. usually will lead to a seal failure. the pump has a relief valve that may have an incorrect spring or sticking piston. <br /> I would get with the rebuilder and have him correct the problem, if any.
Get a mechanical gauge and hook it up temporarily to verify the actual oil pressure. This way you are sure it's not a gauge/sender mismatch or problem.
Sending units match to the gage. Like Don says, check it with a mechanical gage to be sure.That kind of pressure you should be blowing out oil everywhere when you give it the gas or does the PSI stay the same? Have you run the boat yet with the rebuilt motor? Sometimes running a new motor straightens a lot of this type of stuff.<br /> Also like Rodbolt said, the spring in the pump my be wrong, bad or stuck.. Or there could be something left over from the rebuild stuck in there.<br />First though I would check it with a "mechanical" gage to make sure I wasn't chasing a Gremlin.
Are you using a new sending unit with the rebuilt motor? If so, you may have the gotten the wrong unit. I replaced the sending unit on my 5.0 last year with the wrong type, which pinned the gauge, as you describe. The gauge worked fine, after I found the correct replacement sending unit.
