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brak 05-04-2008 03:37 PM

Yanmar oil pressure
This is kind of a chronic issue with my engine. The oil pressure indicator always shows oil pressure either at the low end or below of the normal zone. Oil level in the engine is fine and filters are new, that's where the extent of my knowledge ends. I used it like that for the last 200 hours or so, though subjectively lately it's been even lower than before (or may be not, hard to tell). Why would this happen? How harmful is it?

ronsunni 05-04-2008 04:05 PM

Are you using the proper weight oil for the temp. in your area off operation?
If the oils weight is to low or the engine is running hot this could contribute to low oil pressure.

Faster 05-04-2008 04:09 PM

If in fact your oil pressure is dropping over time, obviously that's not good news. Since the oil pumps are generally pretty robust, reduced pressure will most likely be due to engine wear and increased clearances at bearings etc.

Possibly more likely is a false indication (I'm assuming you are not getting any alarms) I would hope that you'd get a buzzer alarm if any conditions (water temp, oil press, low amps etc) occurred. So if the oil pressure switch is happy, then maybe it's just the gauge itself, or the signal to it. Assuming it's an electrical gauge then you're looking at the transducer as another possibility.

One way to check would be to plumb up a good gauge (say 0 - 100 psig) to the transducer connection and see what the pressure really is. I'd expect anything between 30 - 60 psig depending on temperature. (does your indicator have units on it or just a "normal range"?)

You do need to figure this out.. if indeed you're running low that's not something you should continue to do.

SYMandalay 05-04-2008 04:25 PM

I agree with Faster that you need to find out if the gauge is giving you a correct reading by checking the pressure with an alternative gauge. How many hours are on the engine? A Yanmar should run a looooong time before having oil pressure problems (maybe 7 or 8,000 hours??)


brak 05-04-2008 09:40 PM

The engine has 900 hours on it and I hope that the actual pressure isn't an issue.
Actually converting from what gauge shows in kg/cm^2 to psi I get between 30 and 60 psi, may be up to 80 psi occasionally. The "green range" is between 60 and 120 psi, and the arrow is not usually higher than just above 60.

The gauge is electric, so it may be the gauge, I suppose.

So, what is the normal oil pressure range for these engines?

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