We just built a Merc 454 MPI Mag inboard. Since our block was bad we used a Chevy 454 Gen VI block. The engine runs fine but.... with the remote filter adapter and cooler in the loop, we get 30 psi regardless of rpm. The needle is just stuck at 30 psi. Yes we verified with a mechanical gauge. Take the filter adapter offf and spin the filter right on the block , all is normal. 30PSI idle, 45 to 50 high rpm. We assumed a restriction in hoses or the cooler, replaced all with new, same problem.

we used a 30 psi bypass valve in the filter pad on the block, and removed the center valve under the nipple. This defies logic, the only thing that changes is three or four feet of hose and the cooler. The new oil pump "can" make 45-50 psi, it does so when the filter is right on the block.

This is driving me nuts,,,HELP!!

Dave
Dave

Just guessing but sounds similar to what I had going on, and mine was a high volume pump. Using the standard oil lines and fittings caused a restriction which kept the pressure down. After replacing lines and fittings with AN10, the pressure came up

I think the bypass may be in wrong place and opens at 31. That bypass is to open when filter plugs up. Or a plug needs installed between the 2 factory oil cooler ports.

The hose size is interesting, however the port side of engine uses the same houses and is fine. Could the standard automotive Oil pump not be as strong as the original MerCruiser in the other engine

I was not aware that there are existing ports for an oil cooler. Where do I find these to plug them off?

The standard auto pump is the same as the standard marine. There must be something with the lines and filter head causing a restriction, or your bypass is the restriction

As for the cooler ports, don't understand derekn post my self

​​​​I can't copy paste with this phone. I am also having a hard time finding the article I am looking for. Couple hours I should have something.

after rereading this thread i think you have a restriction in your cooler. apparently oil pressure tap is after oil goes thru cooler. but here is a scoggin dickey writeup on these relief valves and where they go. http://www.performanceboats.com//att...chmentid=85242

Glad to hear standard automotive pumps should be ok,. My concern is the new pump came with a second spring for conversion to high pressure. We did not use it.

Looks like the "ports"mentioned in the previous posts are two threaded ports at the oil pan rail. By removing the center bypass valve, my understanding is that takes them out of the loop.

BTW> all hoses and the cooler are new! I have opened the remote filter bracket , cleaned and inspected. New Delco PF454 filter, also tried quicksilver filter. We replaced the Side bypass valve on the pad with a new 30psi differential valve.

I thought the same thing, restriction. But with all new parts............?

what if you just put a bypass hose in place of the cooler? just a loop out and back in. I think if that showed normal pressure, then there may be an obstruction in the new cooler. just cuz something is new, doesn't mean it is perfect. post 6 in this thread has a good pic with pipe cleaners showing path. http://www.offshoreonly.com/forums/g...ass-valve.html and shows the factory cooler ports. also, if pressure stays at 30 with loop hose imitating cooler, then you know there is an issue in those oil passages at the filter pad. this is a brand new block? worst case scenario, you could screw the filter on down there, and run the cooler to the 2 factory cooler ports.

Interesting issue.

Check to see you have the oil lines routed correct. People have reversed them in the past and screwed things up.