oil pressure problem on 454
 

Hi guys, took the boat out yesterday for a long run in the sun and after 20 minutes the oil pressure started creeping below 40psi, then within another minute or so was at 20psi, then all of a sudden dropped to zero! I was running a steady 3500rpm.

I let the engine cool for a while then limped back to the marina at 900rpm with about 5psi showing.

The engine is fairly standard and has a new slightly upgraded oil pump fitted and has had lovely pressure for the last 4+hours use I have had out of it this season.

The engine is going to have to come out I am sure, but what are your thoughts on what it might be? Am hoping not a cracked block, is that likely?

TIA

Oil level OK? No milky fluid in oil?

Senders can go bad. An engine with no oiling sounds bad pretty quick.

Wannabe

oil level was a little high and no milk, infact very clean.

put a mechanical guage on it ASAP to verify that your OEM gauge is working right. my old outlaw had a flaky oil pressure guage, it read zero sometimes at startup, i would put a jumper wire to the ground on the sender and the guage popped right up to 60 psi every time. you can buy a cheap mechanical one at harbor freight with all sorts of adapters to sanity check your gauge.

if you truley have that low of oil pressure something must be going south and it could be all sorts of reasons. if its truely low first thing i would do is pull the filter and cut it open and look for shaving, debris, ETC and drain the oil and check it for any debris also.

Quick update:

Started the boat from cold yesterday(frist time since pressure problem). Pressure immediately went to 65psi, but as the boat warmed up the pressure fell down to about 20psi hot idle. All sounding good so far, right? Sadly after reaching temp I started to notice a big end knock so will have to pull the engine after all.

Question. Do you think the knock is due to the low pressure, or do you think this might have been the initial cause of the low pressure? Don't want to pull the engine do loads of work only to find the fault elsewhere if you know what I mean!!

I think you cooked the bearing and that caused the low oil pressure. Your going to have to disassemble and these can be impossible to correctly diagnose from description only.

wannabe

Thats what I wanted to hear really. I don't know what else could have caused it.

I'm having similar issues with mine, although after a long cruise I haven't notice a drop while running, I notice a drop to 10 psi at idle speeds. When yours drops does it come up with acceleration or does it stay low?

After a cool down it did increase to a point then dropped off. I have since stripped the engine and found that all the big end bearings were shot, 3 had spun and one had hammered itself out to the thickness of a piece of paper!! i know believe all this started when i hydraulic the motor after springing a leak in one of the manifolds.

Make sure the oil pickup tube is welded to the pump housing.

End result!!

http://i236.photobucket.com/albums/f...K/IMG_2152.jpg
http://i236.photobucket.com/albums/f...K/IMG_2153.jpg

Oh, I didn;t realized you hydrolocked the motor. Did you do a leakdown test of the oil pressure after?

Those bearings are cooked BTW

Wannabe

Now you need to find the cause of the problem. When this happens metal shavings will be everywhere. I have seen them in lifters, valve guides, imbedded in piston skirts, and so on. Make sure every oil passage is cleaned twice. Make sure you get a new oil cooler also and make sure the oil hoses are clean.
Since not much will be left, time to build a stroker engine.:cool:

It's getting the crank reground, new pistons, new rods, new cam, new lifters, new oil pump and pick up and am gonna flush the hell out of everything I am keeping.

Was hoping to flush the oil cooler. Do you not think it can be cleaned?

stroker would be nice, but would kill my Alpha drive I think!!

Strangley after a cool down I managed to get 60psi, but I can see by the debris in the pick up that it was struggling. the pick up was blocked solid causing the pump to bypass!

This time use the Melling 10778C oil pump and make sure to have the pickup tack welded on the pump cover, do this carefully without a ton of heat so as to not damage the pump.
Also make sure the oil pickup is set up about 3/8" to 1/2" from the oil pan bottom when assembling.

Replace the cooler! Replace the cooler! Replace the cooler!

When having the crankshaft reground, have them mag it for cracks or serious flaws, straighten it first and then micropolish the journals after finsish grinding. Obviously balance the full rotating assembly.

Take the time to make sure the oil lines from the adaptor, to the oil filter and thru the cooler and back to the block are plumbed correctly so as to not restrict the oil flow and over heat the oil.
Make sure the shop installs any oil by-pass vlaves correctly and as they were engine was originally installed.

Use a good high wear package conventional oil for 2-4 hour breakin and then go to a good 20-50w performance oil.

Check the main line straightness and have the block aligned bored or honed to correct any problems there with straightness.

Make sure the machine shop doing all the block work knows, uses and understands the correct bearing, end play, rod fitment, piston, ring clearances and such for a marine engine versus automotive application and that they check them during short block assembly and don't just assume they are ok because of machining values and new rods, pistons, rings new bearings and such !

Make sure the engine is assembled with a good engine assembly lube and that is is properly oil primed before starting.

The most critical time on a fresh new machined and equipped engine is at the first startup. If things are not right here, they go bad very quickly and the result is usually a junk engine! Problems here tend not to fix themselves!

Hope everything goes well on the new engine. best of luck!

Best Regards,
Ray @ Raylar