Update - drop in oil pressure

[Colvic Watson]

Thanks for all the replies to the thread on what causes a drop in oil pressure at higher revs. Based on what had been said and the yard's own 'take it carefully' approach they ran up the engine, then removed the warm oil, flushed through and filter change then new oil. Then they carried out a manual pressure test which showed 40psi at idle and 60psi at high revs - personally I don't understand what that means for the engine but the yard are content that nothing else needs doing.

The electric gauge however still shows a drop in pressure at higher revs so they will check the wiring. Maybe all the fuss wasn't necessary but after she had stood for 2 years and only had one oil and filter change on recommissioning, I don't suppose it's done any harm to have another oil & filter change with flush used.

Thanks again everyone for their input, at the very least I understand more about how the engine works. Simon

 

[sailorman]

Thanks for all the replies to the thread on what causes a drop in oil pressure at higher revs. Based on what had been said and the yard's own 'take it carefully' approach they ran up the engine, then removed the warm oil, flushed through and filter change then new oil. Then they carried out a manual pressure test which showed 40psi at idle and 60psi at high revs - personally I don't understand what that means for the engine but the yard are content that nothing else needs doing.

The electric gauge however still shows a drop in pressure at higher revs so they will check the wiring. Maybe all the fuss wasn't necessary but after she had stood for 2 years and only had one oil and filter change on recommissioning, I don't suppose it's done any harm to have another oil & filter change with flush used.

Thanks again everyone for their input, at the very least I understand more about how the engine works. Simon

the pressures look very good, its almost a new engine

 

[RobinBirch]

Simon

Thanks for the closing update and good news that you don't have a major overhaul/engine change decision.

 

[Colvic Watson]

the pressures look very good, its almost a new engine

See, I told you Tom was good.

BTW - is 40psi and 60psi a good spread?

 

[sailorman]

See, I told you Tom was good.

BTW - is 40psi and 60psi a good spread?

40 on tick-over is very good

 

[Bosun Higgs]

The electric gauge however still shows a drop in pressure at higher revs so they will check the wiring.

At lower speeds, does your guage register the same numbers that the yard's guage did> If it didnt can you pro rata your guages readings so that you kno what the p[ressure actaully is dropping to at high revs ( eg if your guage is underreading by 20% at normal revs and reads 30psi at higher revs then that suggests a real pressure of 30 plus 20% = 36psi)?

I havent read the earlier thread. I would doubt that the wiring is at fault - thats much more likely to cause no reading at all than a wrong one and only at certain revs.

 

[Colvic Watson]

At lower speeds, does your guage register the same numbers that the yard's guage did> If it didnt can you pro rata your guages readings so that you kno what the pressure actaully is dropping to at high revs ( eg if your guage is underreading by 20% at normal revs and reads 30psi at higher revs then that suggests a real pressure of 30 plus 20% = 36psi)? I havent read the earlier thread. I would doubt that the wiring is at fault - thats much more likely to cause no reading at all than a wrong one and only at certain revs.

I don't know about the gauge readings, I'll check this weekend. Meanwhile: http://www.ybw.com/forums/showthread.php?t=294491

 

[BGW]

something in the back of my mind is saying that US vs UK gauges work in the opposite way - with regard to the resistance - Has the gauge or the sender unit been replaced with a non matched partner? - If I am right then would this cause the gauge to run 'backwards'?

 

[Trundlebug]

That's great news on the pressures, it certainly sounds quite healthy from the figures you've given.

The only explanation I can think of for the indicated drop in pressure would be a slight stiction in the oil pressure relief valve.

As the revs rise, the pressure rises, but to open it initially and overcome a slight sticking OPRV the pressure rises above 60psi to say 65-70 psi, then drops down to its intended pressure of 60. Not sure if that would concur with what you're seeing on the gauge?

Overall I wouldn't do anything further, as the mechanical gauge readings confirm it's all healthy.

I would just treat it as part of the character of the boat, "it's just what it does" and only become alarmed if anything changes significantly.

 

[PCUK]

The mechanical gauge has told you the engine is fine. Check or change the electrical gauge and sender for proper peace of mind.

 

[Colvic Watson]

something in the back of my mind is saying that US vs UK gauges work in the opposite way - with regard to the resistance - Has the gauge or the sender unit been replaced with a non matched partner? - If I am right then would this cause the gauge to run 'backwards'?

thanks for that and all the other suggestions.

Armed with the two threads I went on board yesterday and turned on the ignition. The temp needle stayed where it should at zero, the oil pressure needle shot up to max! I started the engine and the needle settled at about 65psi, revved the engine and it dropped to 25psi! It's blindingly obvious that BGW is right. I'm now a bit peed off with the yard who have been outstanding so far - the moment I turned the key to the first stop and saw the oil pressure gauge flick to max psi I could see what the problem was. I think a polite preemptive email is in order before the bill is written for all their investigations

Thanks again everyone.