Weird Oil Pressure Issue
 

I am having some werid oil pressure problems. Brand new 502. Tyler Crokett built.

It builds great oil pressure at Idle (40-50), and for the first few minutes on plain (50 @ 3500 rpm), but then starts to fall. It will keep falling until I back off. When it first starts to fall, I can back off to 2900rpm and the oil pressure will come back up to 40psi, but slowey I have to pull back to 2600rpm to keep it from falling. If I back off plain, pressure imediately comes back up to 40psi or more.

Called Tyler and he wants me to bring it back for them to pull it and check the relief valve but before I do that I thought I see what others have to say.

I've noticed the oil never comes up to temp. 180deg is the max I ever get. Could condensation in the oil be causing something like this? I really hate the thought of being out for most of the season AGAIN this year!

Unless you have the crankcase milkshake thing going on, probably not. You should have an oil t-stat on the boat though.

I wouldn't screw around- if you smoke the motor, Tyler probably won't help you.

Here's a great way to educate youself on oiling systems. If you read this, you'll be able to have an informed conversation with Tyler. http://www.offshoreonly.com/forums/s...3&page=1&pp=20

Yes there is an oil t-stat

my god man ...take it back ....however ...is this electric gauge? .....but I would let Tyler handle it ....

Tyler did ours as well. He also installed after-market oil coolers that kick on at 180*. The oil hits that temp, the gates open, and the oil drops below 180. Never seen it higher than that. We also had some strange oil pressure issues with one of the engines he built. After the engines warmed up, the warning light in the gauge would start to flicker and the needle would also flicker in synch with the warning light. I added a manuel oil pressure gauge in the bilge, so when I had issues with the electric gauge, I could crack open the hatch and check the real oil pressure.
Carder

180 degrees is where you'd want an automotive engine to run at. You need to break 212 on a boat to cook the moisture out of the oil.

Yep, that's what I thought.

I went ahead and took it back to Tyler. This engine has been a nightmare. It's been down three times since I had it built last year. I'm 20K and 13 months into this project and I still don't have a boat that will reliably get me anywhere. I just hope this is the last time I have to be down. I didn't ask for a flaky race engine. I wanted something resonably conservative and reliable. :(

Was he able to put a higher temp thermostat in for you?

Did Tyler dyno test the engine after he built it???? If so, were you present during the dyno session and what was the oil pressure reading from the dyno test? From what I have heard about Tyler he is a pretty smart guy---I am sure he will figure out the problem and stand behind his work. Be sure to keep us posted.

Is the oil going thru the oil cooler or bypassing the cooler? Are you reading the oil temp in the pan or somewhere else? Sounds like classic need oil cooler.

Other option is not enough oil in the pan? Or too small of a pan?

bcarpman,
He apparently wanted it at 180*... if he changes yours, let me know.
Carder

Well, Tyler got to it pretty quick this time. Unfortunately, he found nothing wrong internally. Checked the pump, bypass, pickup, pan to pickup clearance, dipstick level, cut open the filter, even pulled a couple bearing caps.

He did find a lose ground wire that his FORMER installer had forgotten to tighten, but the problem wasn't intermitant. It was very consistant with engine rpm and load. I have a hard time believing a bad ground could cause such a consistant problem with only one gauge (all the others are perfectly consistant)

Yikes, nothing I hate more than a problem without a known cause. I'm going to drop it in tomorrow and see. Going to hook up a mechanical gauge just to make sure.

He also said he wants to use the 180 deg thermostat, so I guess I'll stick with that.

It was dyno tested after the original build last may (2007). but it's been apart twice since then for other issues. When it was initially dynoed it made really good oil pressure. I don't have the sheet on me, but I think it was like 60psi at that speed.

I wonder why he didn't do a pressure test FIRST with a mechanical gauge,it easy to second guess someone but I would have cut the filter open then if it was clean put a mechanical gauge on it next before the ripping began. Either way I hope he finds the problem and solves it for you,Smitty

I work for an engine machine shop that deals mostly with drag racing and high end street cars, but the same principles of an internal combustion engine apply. Anyways, I've seen that exact thing happen a number of times when there isn't a sufficient oil pan on the application. What I mean is, we'll have a customer that has a small block stroker with a high volume oil pump and a stock oil pain and at WOT, the oil pressure will hold for a second and then start to drop as there isn't enough volume of oil in the stock pan. it needs something aftermarket that holds more quarts b/c it is pumping it faster than it's draining back and getting to the pickup again. Maybe this is something for you to look into. Hope it helps.
Barry
www.ProLineRaceEngines.com

Not a bad thought ..... on the Dyno you get just a few seconds of WOT pull and its over ...
I wonder what his thinking is on 180* stat? ... I know on my motors until we got the temps up over that 200 mark there was milk on the valvetrain ....m

This does sound like it is running out of oil! Pan could be the problem.

I agree, we had a similar problem with the first couple 383's we built. Insufficient oil levels, or an improperly placed oil pump pick-up. Either way it sounds like it is siphoning the pan dry, or the pick-up is placed to high. Thats just me pulling one out of my rear.....

I agree with the running out of oil theory...If they went to a high volume oil pump you need a 10 quart pan.

I too have seen the same problem. How big is your oil pan? I'm running 10 qt Canton pans and no problem.

I experimented years ago with a small block. I removed the windage tray on the stud kit and ran without it and it did the same thing. I have been told on more than one ocassion and reconmended to remove the tray I know better. Also, when i changed everything over to -12 with larger coolers and filter I filled them with oil in addition to the pan so I wouldn't suck the pan dry

Well, we took it out for a spin with a mechanical gauge hooked up. The electronic guage was reading a little low, but still stayed around 60psi on plain. Tyler thinks it was the loose wire, and I can't say otherwise, but I still can't figure out how a loose wire would show such a consistant oil pressure issue and not effect the other gauges.

Regardless, I'll just be happy if I don't have any more issues, but not knowing the cause for sure makes me hesitant.

Now if only I could figure out why the boat only gained 5mph going from a stock 330hp 454 with 1000 hrs, to a 550hp 502!! Time to experiment with props AGAIN.

So what did the mechanical gauge say as compared to the electric one?

Thanks Nordic95

For the most part it was within 5psi. The electric gauge must be electronically damped so it followed changes in pressure slower than the mechanical gauge. Either way, it didn't justify the 20psi readings I was getting while on plane.

bcarp,

Sorry to hear you are still struggling...It sounds like you are on the water now and I hope you don't have any more problems.

Just my .02..... I would have agreed with running out of oil at the pickup, but I had a similar problem in the past. I had a little Jet boat with a 550hp SBC in the back in the day. One time I had the exact same symptoms and it turned out to be a loose sending wire. I never beleived it would act the way it did, consistantly anything over 4g's the guage would fall out, but after tightening it there were no more issues.

Did you ask about the 180deg thermo? I still wonder about that. I see the point in using a 212, but then again, I don't know that stock Mercruiser engines have an oil thermo at all, so I don't know what to think. I am also running a 180deg and no probs so far.

Keep us posted, hopefully you will find the speeds you are looking for.

Tyler wants to stick with the 180, so that's what I'm going to do

I had a loose sending wire too. (After I got it back from Tyler :D) Not his fault as I did the install and it probably got bumped a bunch of times. The oil pressure gage did all kinds of strange things.The problem drove me nuts. Verified it had pressure with a mechanical gage then finally found the connector to the sending unit is a push on type. Just needed to crimp it a little tighter and problem was gone.

You should've seen what my tach did when I had a loose ground on an engine. It was reading 1000 high during a poker run. I thought I was overrevving until it fell off. :rolleyes:

Try a Fram HP series oil filter and check your oil lines, they might be reversed.