Oil Pressure Levels

[Danfarry]

I've had a search on the forum but can't find an answer. Boat has twin Yanmar 4LHA-STP engines.

When I start the engines the oil pressure is just above half way. This stays the same as the engines warm up. Once engines are warm and I increase the revs the oil pressure increases slightly on what it was when starting from cold. After a day out on the water at various speeds and with the engines thoroughly up to temperature, the oil pressure is lower at idle than it was when the engines were cold.

My question is, as the oil warms and the viscosity increases, does this lead to a fall in pressure?
My opinion is that this should happen, just want to confirm this is correct or if I have a problem.
The oil pressure is the same on both engines throughout the cycle of use.

 

[andy59]

Yep , oil is thicker when cold so pressure drops when warm . My tamd75s idle at 60 psi cold and about 35 psi hot .

 

[volvopaul]

I've had a search on the forum but can't find an answer. Boat has twin Yanmar 4LHA-STP engines.

When I start the engines the oil pressure is just above half way. This stays the same as the engines warm up. Once engines are warm and I increase the revs the oil pressure increases slightly on what it was when starting from cold. After a day out on the water at various speeds and with the engines thoroughly up to temperature, the oil pressure is lower at idle than it was when the engines were cold.

My question is, as the oil warms and the viscosity increases, does this lead to a fall in pressure?
My opinion is that this should happen, just want to confirm this is correct or if I have a problem.
The oil pressure is the same on both engines throughout the cycle of use.

Yanmar shows low pressure on gauge , Infact its well within its limit as in past I've fitted a pressure gauge that actually shows the figure unlike the stupid gauge they supply that only a monkey can decipher .

 

[Danfarry]

Thanks for the replies, it's reassuring. The gauge is a little vague..

 

[PeterBoater]

Some Yanmar oil pressure senders are notoriously inaccurate after a few years, are very expensive to replace and do not last. Having apparently low pressure readings, I bought a free-standing diagnostic pressure gauge, with lots of thread adapters, on Amazon for less than £20, which showed that pressures were in fact well within specification, so I did not replace the senders. It is possible to buy other, very much cheaper, senders that will fit, with or without new gauges, from the likes of Faria or VDO, but it is a complicated area, with European and USA types; one type increases electrical resistance with increasing pressure, the other type decreases resistance, then there is the initial resistance and thread type (thread adapters might be required but are available). Fortunately, having established that my actual pressures were OK, I didn't have to go down the sender replacement route.