Oil Pressure Gauge

[Five O'Clock]

Is it normal for my oil pressure gauge to be hovering just above the zero mark at idle, then as I increase throttle the gauge the needle steadily jumps back up around 40 psi.

Is this normal, or when I start the engine, it should be around 40 no matter what?

 

[oops!]

Re: Oil Pressure Gauge

nope.....you want good oil pressure all the way around....check the oil pressure sending unit...and the gauge.....if thats good....you might have a slightly spun bearing

 

[QC]

Re: Oil Pressure Gauge

You should probably post this in the appropriate engine forum . . . I/O or four cycle OB . . .

 

[Five O'Clock]

Re: Oil Pressure Gauge

thanks, posted there!

 

[Kev144]

Re: Oil Pressure Gauge

Is it normal for my oil pressure gauge to be hovering just above the zero mark at idle, then as I increase throttle the gauge the needle steadily jumps back up around 40 psi.

Is this normal, or when I start the engine, it should be around 40 no matter what?

Should be fine. Look at cars. When sitting at a stop light, idling, the oil pressure drops low but when driving anything above an idle, it increases.

 

[Silvertip]

Re: Oil Pressure Gauge

Low oil pressure at idle is not necessarily "normal". An oil pressure sender in a car will trigger the oil light at about 5 - 6 PSI and the same holds true for the current generation of 4-stroke outboards. Idle oil pressure depends on the viscosity of the oil and oil temperature. If you have just made a very long run at high throttle settings, oil pressure may indeed be a tad on the low side but again, if you were running full synthetic, that may be normal. If you are using conventional multi-viscosity oils, oil pressure really should not drop to anything below 10 - 15 pound on an otherwise healthy engine. If it does, it is probably due to the fact that this is a high hour engine and bearing clearances are opening up a little. An engine with very little oil pressure at idle but normal pressure at off-idle and higher may run for a very long time but you do need to keep an eye on things. Contrary to popular belief, low oil pressure is rarely due to a bad oil pump.

 

[wca_tim]

Re: Oil Pressure Gauge

it also depends a lot on the way the engine was built, where the pressure is being taken, and what kind of an engine it is... the type of oil matters as well. spec for a i/o is 10 psi per 1000 rpm/s - the same that is given in a number of books I have or have read on high performance small block builds. A well built small block marine / performance engine running synthetic oil will show almost no oil pressure when idled down to 600 or so rpms - especially if you take the oil pressure off the port on the front of the block. it's also important to remember as several others have noted that factory electric oil pressure gauges are not always the most accurate. before going into a panic one way or the other it is a good idea to check it with a mechanical gauge.

 

[Silvertip]

Re: Oil Pressure Gauge

A marine engine is as close to a truck engine as you can get, and truck engines do not normally idle at zero oil pressure -- with or without synthetic oil. I have owned GM trucks for decades and when worked hard they never idle below 20 PSI (typically 30 - 35 PSI) and all have seen nothing but Mobil 1 full synthetic. While I do agree that oil pressure will depend on how the engine was built, however if it is a low hour standard marine motor and it idles at less than 5 PSI, I would be having a serious chat with the engine builder.

 

[wca_tim]

Re: Oil Pressure Gauge

agreed! no oil pressure or below 10 psi on almost anything and below say 20 in most situaions, indicates a significant problems. I was making the point that the answer in a broader sense really "depends" on a lot of factors, but you're post is right on the money.

All the books, manuals and "guru's" I know cite 10 psi per 1000 rpms or more and your fine.

A marine engine is as close to a truck engine as you can get, and truck engines do not normally idle at zero oil pressure -- with or without synthetic oil. I have owned GM trucks for decades and when worked hard they never idle below 20 PSI (typically 30 - 35 PSI) and all have seen nothing but Mobil 1 full synthetic. While I do agree that oil pressure will depend on how the engine was built, however if it is a low hour standard marine motor and it idles at less than 5 PSI, I would be having a serious chat with the engine builder.

 

[Five O'Clock]

Re: Oil Pressure Gauge

thanks guys, i am running with the volvo full synthetic oil... check out one of my last posts when I moved it into the volvo forum... here's the story:

http://forums.iboats.com/showthread.php?t=270803

"first, I have about 110 hours on the engine.

second, here's what happened:

I spent the day on the boat, tubing and cruising around with family. after about 5 hours of operation, I was taking the boat back to port, cruising around 3100 RPM's when the engine shut down and the alarms started going off... checked the gauges, and the oil pressure gauge was at zero.. shut the boat off completely, anchored, had sea tow bring me back to port... opened the engine hatch, oil everywhere... got down inside noticed one of the hoses coming off of the oil filter was completely blown off... I detached the hose and brought it to our local volvo penta dealer... They had said that this hose was recalled a few years ago and there was an adapter kit for both tubes, the oil flowing from the reserve to the filter, and the oil flowing from the filter to the reserve.

I changed the hoses out, did a complete oil change, and started running again. no unusual noises from the engine, everytime I check the oil it's at "safe" level, never "add" level.

I do remember the oil pressure gagues were always at 40psi before the hose blew, even while running at idle. Now, when i'm idling, it's around 10psi then as I increase throttle it eventually hops back up to 35-50ish...

any thoughts on this??"


that's the story of what happened

 

[Silvertip]

Re: Oil Pressure Gauge

You will likely get the same answers here that you got before. You ran the engine without oil. Rod, main, and cam bearings don't like it when there is no oil pressure and they can be damaged in a short time. You took some life out of the engine by not keeping an eye on the oil pressure. That gauge and the water temp gauge are the two most important gauges on a boat. Ignore them and you get to deal with the problem you are now faced with. I wish we could fix the problem with words -- but that isn't going to happen. And just so you understand, "oil pressure" and "oil level" are mutually exclusive. The engine can have the proper amount of oil in the crankcase and still have no/low oil pressure. Without oil however, you cannot have oil pressure.