Sudden oil pressure decrease
 

Looking for some pointers!

I have twin 454s with 15 hours on them. They both pushed identical oil pressure at all times. After a few WOT pulls at havasu this weekend, the right motor dropped to half the normal oil pressure.

Left engine hot oil
idle @ 40psi.
70+psi at higher rpms

right engine hot oil
idle at 18psi. Sometimes as low as 15psi
40psi max at high rpm.

I replaced the oil pressure sensor, and it shows the same results. What else could have broken? Any help is appreciated!!

No expert here

when you say oil hot
how hot is hot?
180 degrees? 200? 230?

but 70 plus pressure in a stock ish 454 I have never seen that b fore

although 40 is not so high either
i would test reality with a mechanical gauge if you can

i am sure some motor guru here will chime in and share their thoughts

I would take the lower pressure engines oil filter off and cut open for inspection.

Time to call the engine builder and see what the nexts steps he wants you to perform.

Hopefully this book does not appear in the mail

https://cimg9.ibsrv.net/gimg/www.off...0ebc83d1f.jpeg

You could have some oil pump issues.

The relIef spring may have partially failed.

Your oil is hotter for some reason, dropping viscosity and dropping oil pressure

Oil pump pickup blockage?

Oil cooler blockage?

Fuel dilution of the oil?

Best COA as mentioned, is to check oil and filter for contaminants.

And do this before you run it even another second. Could be something as simple as a stuck relief valve in the oil pump or it could be . . . . . . . :(

Thanks for all the quick replies!
I poured some oil out of the old oil filter, and it had more glitter than a stripper's eyeshadow. I was hoping that the oil filter was clogged, and that was causing the pressure to drop. It looks like that engine is properly f@#$ed. It has about 45 minutes of run time after the issue started. It never lost power, got hot, or made any ticking noises. I think a bearing has partially failed. I'm pretty damn impressed that it remained up on plane and making power with that type of failure.

Since there isn't a catastrophic failure, I'll yank the motor and clean it/rebuild it with the same internals. It should just need a good cleaning, new bearings, rings, and gaskets. I don't want to upgrade anything and have asymmetric power.

Did you build the engines ?

I did not personally build them. They were built by a performance shop in Washington, NC in 2016. I bought the boat in 2022. I already asked the previous owner, and there are no blueprints or tech data on the motors. They were built in a handshake deal, probably on a tight budget. They supposedly had 15 hours on them when I bought the boat.

Depending on what you find, you might need to prepare to do both, sorry to say.

I’m sending off an oil sample today to try & find out what broke. I’m mentally prepared to yank this motor and rebuild it.

Thats probably a waste of money. You know it has to come apart anyway. You will find out soon enough what failed.

Agreed, it's coming apart regardless - save the time and money from the oil analysis on pulling and tearing apart the engine

It was $40. I sent it in today. If nothing else, it'll keep me entertained and satisfy my curiosity. I'm moving from CA to Houston TX in 4 weeks. There's no sense in pulling the motor right now. I'll just wait until I move, then pull it for an autopsy.

Make sure you thuroughly clean all oil passages in the block, crank, and replace or flush the oil cooler whatever you do. The debris from previous bearing failure will wipe out new bearings with a quickness.

DO NOT reuse the oil cooler. Getting it all cleaned out is 50/50 at best. Probably what happened is they reused it before.

Chris

If you didn't already, I'd send in the "good" engines oil for analysis since you have no history on it either could be a time bomb also.