jimjomack

Oil pressure problem. I have a pair of 502 MPI engines that were both just rebuilt, new bearings thruout, new pistons, and heads. I also installed a new Moroso blueprinted oil pump. The pickup tubes were welded on. engines were primed correctly until oil flowed out of each rocker arm. They are Crower roller rockers. I started the engines at home and they ran for 15 min at idle and with 30 weight oil the oil pressure guages showed 30 to 40 lbs pressure. I then changed the filters and oil to 20w -50. Upon taking the boat out for a test spin. I had 30-35 lbs of oil pressure upon leaving the dock. After 15 min of running the oil pressure on both gauges were down to 0 lbs. They both lost pressure at about the same time. The water temp guages read about 180 and are constant. I idled back to the dock on one engine as after I let it sit for a while It had about 10 lbs of pressure. Neither engines were Knocking when pressure went down to 0. When I got the boat back home on the trailer and flushed them the guages showed 20 lbs and a mechanical guage I hooked up showed 25 lbs. Ran the engines for 1/2 hour and there is no knocks but only the low oil pressure. Could the brand new Moroso blueprinted oil pumps be bad? On is this some other kind of problem. I am open to suggestions as I already lost the entire season waiting for these engines getting rebuilt.

Thanks, Jim

Audiofn

This is going on with both engines? I would call up Moroso and see if they have a known problem with their pumps. I highly doubt that you have two bad ones unless they have had a bad run. Sounds to me like they may have the bearing clearences up to much causeing your low oil preasure. Who did the rebuild? I would give them a call and get them on it right away. With that weight oil you should have much higher preasure then that even at start up and more so when warm obviously.

Jon

blue thunder

Chisel open the oil filters and look for the flakes of death. Zero oil pressure and no knock do not jive. Hopefully you have an oil pressure sender problem of something similar. Cutting open oil filter will tell the story.

BT

alcor

Here's my 2 cents. Check to make sure you have the oil lines correct from the engine oil adapter plate to the remote oil filter. Center of oil filter hose to center of adapter plate. If they are reversed, you will get partial or no oil pressure due to the rubber skirt (check valve) inside the oil filters. Easy to get the lines crossed if someone wasn't paying attention when they were re-installed after the rebuild. Don't ask me how I know this as I really don't want to admit it.

Al

Krumbsnatcher

I agree with alcor! and if that does not does not do the trick then if those 502's are GenIV blocks ask your engine rebuilder if he repluged the oil galleys under the crab plate for your lifters. Alot of machine shops remove these plugs and unless you remember to put them back in you will lose pressure.

But I still think your lines are reversed!

WILDTHING TAZ

MY 2 CENTS. I BOUGHT BLUEPRINTED PUMPS AND STILL HAD TO PUT A WASHER SHIM IN SPRING TO GET MORE PRESSURER.I WOULD CHECK OIL DIRECTION FROM ENGINE TO FILTER TO COOLER BACK TO ENGINE. JUST TO MAKE SURE YOUR CORRECT.

PatriYacht

What thickness washer and what is your pressure now. A lot of Mercs. only run about 45 lbs. new right from the factory. Always made me nervous.