Oil Pressure gauges

[KREW2]

I have a pair of 125 Yanmars, recently the starboard oil pressure guage has been showing a bit low on tick over. Revving the engine bought it back up, but a couple of weeks ago it was just reaching the green marks. The engineer said it is quite possibly the sender that's faulty.
The back of the gauges is very accessible and I was wondering if could do any damage by swapping the wires from the STB engine over to the perfectly functioning port engine panel to see if the sender is the problem, or the gauge itself.

 

[geem]

Just swap the senders over

 

[KREW2]

I suppose I could. But the wires would be less messy, and not so hard to get to.

 

[geem]

I suppose I could. But the wires would be less messy, and not so hard to get to.

Are the engine blocks wired together through a common negative? If they are you could likely swap the wires over but I would want to to check the engine wiring diagram first

 

[KREW2]

Are the engine blocks wired together through a common negative? If they are you could likely swap the wires over but I would want to to check the engine wiring diagram first
[/QUOTE]

Not sure, there are two 1 2 both Off switches which can start 1 or both engines.

 

[VicS]

Are the engine blocks wired together through a common negative? If they are you could likely swap the wires over but I would want to to check the engine wiring diagram first

Not sure, there are two 1 2 both Off switches which can start 1 or both engines.
[/QUOTE]

If you can swap all the wires over from one gauge to the other there should be no problem. If it means having loose wires floating about make sure they are insulated and make a good diagram of how they are connected before you start.

Personally I'd swap the sensors but if the access is not so good fair enough.

There is always the possibility that the oil pressure on the stbd engine is low so there are three unknowns.; gauge, sensor or oil pressure . You may still have to swap the sensors to reach a final conclusion.

There are wiring diagrams in the owners manual

 

[QBhoy]

Could be the gauge..hopefully. But first thing I’d be checking, is the engine oil itself. See if there is any sign of diesel in there and thinning the oil. Perhaps I’d also check any oil interfaces where it might lose pressure into another environment..like at a cooler and lost pressure into the cooling water side.
perhaps she’s alternatively running a little hot and causing a thinner oil condition?

 

[Sandy]

I suppose I could. But the wires would be less messy, and not so hard to get to.

Fault finding is a process of elimination. Swapping the senders over will prove if it is the sender. Swapping the wiring will prove it is the wiring and swapping the instrumentation. will prove ...

It takes time and needs to be done methodically.

 

[oldgit]

Some thoughts.
Search the interweb.
Many concerns about low oil pressure worries on Yanmar engines going back for decades .
In the main it seems to be the 4 and 6 cylinder engines with "Yanmar" gauges.
Usually worries after noticing very low oil pressure from the gauge on tickover.
The low pressure alarm does not sound.
Check out any of the boating websites that have dealt with this concern before.
The sender unit usually gets the blame but at £180 pounds and no obvious budget clone item around ,its an expensive way to end up with the same result.
Some folks even found it cheaper to replace and fit 2 x new gauges and matching senders to reassure themselves nothing was wrong.
Need to ensure the male threads on the senders are the same as the female threads on the Yanmar engine block otherwise having to find some adaptors.
It has been suggested that the oil pressure at tickover is checked with a seperate oil pressure tester and if pressure within limits , just carry on.
One of the skippers who posted about this had a pair of Yanmars with 4000 hours on the clocks..

 

[NormanS]

When I had a similar problem, I temporarily fitted a mechanical guage.

 

[KREW2]

I have been giving this a bit more thought, if I swap the wires and all functions normally I can eliminate the sender, and assume the gauge is at fault.
If however, it shows low pressure I can then assume it is either the sender, or something else at fault.
If this is the case then I will get and engineer to do a test for me.
Thanks for the replies.

 

[Irish Rover]

I don't know how old your engines/gauges are but I discovered some time back that the glue holding the glass on the gauges on my flybridge was progressively failing - Yanmar engines with VDO gauges which I believe were fitted originally. It started with one temp gauge reading low and later an oil pressure gauge on the other engine wasn't always resetting to zero when turned off. I knew the readings were spurious as I have a separate readout on my chartplotter. I've just bought 4 new gauges which I'm planning to fit this week - if you need to replace any gauges don't buy Yanmar, they're a rip off.