High oil pressure? 5.7 with 10 hours

[LAC_STS]

I just changed the break in oil out of my new engine at the 10 hour mark.

The place I bought the engine from said to use straight 40 weight. The manual calls for 30 but I live in south Florida and will be changing the oil again before the fall after another 50 hours so I followed what they said and put straight 40 in it.

Before the oil pressure would be 35 or so at idle (650 RPM) and about 65-70 at 4K RPM. This is with thin break in oil in it. (Dont know exactly what kind they just said they put thin break in oil in it for the first 10 hours)


Now it has 60 at idle and goes to 80 at 2500 RPM. I haven't ran it yet this was all at the dock in neutral so I didn't want to go up any more in RPMs.


Is this too high? Should I take the 40 out and put 30 in it?


Thanks

 

[Kainon]

Re: High oil pressure? 5.7 with 10 hours

I'd pick up a Good Mechanical Gauge, and install that in the engine compartment as a backup, gauges can be inaccurate and fail to the point that say you Truely have 40psi.. I've seen broken gauges show 10psi, then shutdown start up shows 6psi, but no problems with the engine.

So gauges can be off +- 10% typical,

I dont feel 80psi is too high, I'd say you have a nice tight engine and they may have rebuilt with tighter tolerances on the crank mains and rods.

Being S. FLA with the temps down there, I think 40w's good, where 30w might be a little weak at higher temps.

If you wanted to get crazy, you could add a Oil Temp and Oil Cooler, then I'd think about 30w.

no expert, just know enough to be slightly dangerous.

 

[Silvertip]

Re: High oil pressure? 5.7 with 10 hours

Who knows what oil pump was installed in this engine. It may be one with a stronger pressure relief spring -- hence higher pressure. 80 psi is not dangerous but anything more than that begins to sap power and stress the oil pump drive components. In comparison, my GM Yukon with 112,000 miles idles at 55 psi and at highway speed is 70 PSI with 10W-30 oil in it.

 

[xeddog]

Re: High oil pressure? 5.7 with 10 hours

I have replaced my 5.7L OMC Cobra engine twice now. Both of the replacement engines pretty much peg the oil pressure gauge but I think it has to do with the oil pumps that were installed. The original was probably a "normal" pump, but with my replacement engines I requested the "high volume" oil pump and now my readings are the same as yours. I would think that all is well.

Wayne

 

[LAC_STS]

Re: High oil pressure? 5.7 with 10 hours

Can I ask why you had to replace your engine twice?

 

[Matt89GT]

Re: High oil pressure? 5.7 with 10 hours

I'm running a fresh 350 also, and upon startup it runs about 60 lbs and its pegged at 80 pounds at WOT, at idle after running it hard it will drop to 55 pounds is the lowest I have seen it at idle. I'm running amsoil 10w-30 formulated for marine use. I pulled the engine at the beginning of the season because I lost oil pressure above 3000 RPM's to find the pickup tube layin in the pan so I installed a stock melling oil pump so I would know what I have, and I'm still running those high pressures with a stock pump. I'm thinking where it's a new engine and the clearances are still super tight thats the reason for these enormous pressures.

 

[xeddog]

Re: High oil pressure? 5.7 with 10 hours

LAC_STS - In a word . . .risers. For the first engine, it lasted about 20 years and then the risers (and the exhaust manifolds too) just rusted out and water got into the the exhaust and on into the engine. You'd have thought that I would have seem some performance problems, or watery oil, but I never did until the last. By that time, the risers were so rusted that there was hardly any metal left between the water jacket and the exhaust. When the engine was shut down, the water would run into the exhaust and sit there. The ports in the exhaust manifolds rusted and also the mating surface of the block. So badly that machining was out of the question. Needed a complete replacement.

The second engine was a riser problem too, but this time the engine only lasted about 10 hours. They came loose shortly after installing it, and again water just started pouring into the engine. The last time I was out in the boat, I noticed some smoke in the exhaust and I'm thinkin that ain't good. A little while later we were just about back to the dock and when we went to idle the oil pressure fell almost to zero. Not that REALLY ain't good.

I never did see watery oil at any time, but when I took it in for a tune-up at about 7-8 hours, the mechanic said I had water on spark plugs 7 and 8. We had had some pretty heavy rain and so attributed the wet plugs to the rain. Last time we came back in I let the boat sit for a couple of days in the sun, and still had water on the plugs, but this time it was all of them except 1 & 2.

When I picked up this last rebuild, the mechanic told me that what ever I do, make sure I re-tighten the riser bolts and re-torque the exhaust manifold bolts the first 3 or 4 times I come back in. Wish I had known that last time!! Sure enough, the first time I come back in the riser bolts are . . . I don't want to say loose, but definitely NOT tight. Exhaust manifold bolts were probably a couple of ft/lbs loose too, but not bad. The second time I came back in, sure enough the riser bolts are a tad loose again. Not as bad as the first time, but definitely not tight. Exhaust manifold seemed ok. Third time in, I think they are finally holding. Will have to wait and see about the fourth time I come back in.

So that's my story and I'm stickin to it.

Wayne

 

[Bifflefan]

Re: High oil pressure? 5.7 with 10 hours

Now it has 60 at idle and goes to 80 at 2500 RPM

Sounds right for changing to a higher weight. Go with what the engine manufacturer says, they are the ones that do the testing and the ones that can tell if your running the wrong weight oil when you take it in for a warranty replacement because the bearing have wahed out from to much pressure.
80 is not high but getting there.

Rule of thumb is 10 psi per thousand RPM over idle speed.

 

[LAC_STS]

Re: High oil pressure? 5.7 with 10 hours

Ok so I took the boat out today/tonight for a couple hours.


Before I had only started the engine at the dock and watched the pressure at idle in neutral and revving it in neutral up to about 2500 RPMs.

When I took it out the oil pressure eventually did come down to about 50 at 1500 RPMs and about 70 at 4000 RPMs. It never pegged on the gauge. The gauge goes up to 80 PSI. The needle can go a little further than 80 but even when I was accelerating and giving it a lot of throttle it would only sit right before 80.


But as I was driving a little later I noticed something that it did before I changed the oil. The pressure on the gauge went down to about 35 PSI then when I backed off of it down to about 1500 RPM it went down to 20. Then when I hit the gas again it went back up to 60 PSI.

I dont know if the sender or whatever is bad but I am pretty sure it came new with the new engine. I will have to ask my friend Im sure he remembers.

I bought a mechanical gauge but have no idea on how to hook it up.


Also when I was driving the boat started hesitating like it was gonna die. It actually did die once and I noticed the VHF said low battery so I went and looked at the batt switch and I had actually left it on #2 so I put it back to #1 which is what I usually run it at. I checked the alt and it was reading almost 14V so I don't think its bad but on the V gauge it said 12. It used to be at 14 with the engine running. I did have the radio and stuff on for about 10 hours over the 2 days I was trying to get the stupid oil filter off.

After I switched to the other batt it fired right up. But I kept hearing what sounded like little backfires. Like little pops or something. Im pretty sure it was back fires though as it sounded like bubbles or it coming out of the exhaust.

It would run great and then it would start cutting out.


Is there any way this could be related to the oil or the oil pressure? I thought the oil thing was gonna be fine the first hour or so I was out because the oil pressure was at about 75 when I was about 5/8 throttle. It wasnt pegging or going at 80 or more. But all this has me worried. I checked in the bilge a bunch of times and there was no oil in it.

Here is the mechanical oil pressure gauge I bought but dont know how to hook up after reading the directions.

It says something about needing an adapter and a tee fitting. Is this stuff I have to buy or what. It gives different kinds of directions for different kinds of senders. I see one on the top of my engine that looks like the one in the pic but maybe the sender is the thing that is above where the oil filter goes with the wires connected to it? I dunno.


Any idea? Suggestions? Sorry for the long post. I appreciate it.