Mastervolt whisper 3500 generator low oil pressure shutdown in the Caribbean

[davethedog]

Hi all, and yes this is a real first world problem!

We have a Mastervolt Whisper 3500 generator fitted (was on the boat when we bought her in the Uk) and now finding that after a few hours of running it will sometimes shut down and give a "low oil pressure" warning on the display. The oil level is checked and all good and we never had this issue in the UK before we left. I have changed the oil pressure sender today and it ran for about 80 mins then gave the same error. Have just cleaned out a small amount of stuff from the water intake filter and changed the impeller (the old one looked fine to me but changed it anyway) and removed the engine side case and opened the engine bay and has been running for about 2 hours so far. Obviously running it with the case off ands the engine bay open is not ideal!

Would this be due to the increased water temperature here making the oil too thin?

If so, would changing the oil viscosity to a thicker oil help? Current oil is Multigrade 15/40.

Apologies if this seems a stupid question but when I have been in places around the world using 4x4s etc they usually have a different oil than in say the UK.

[SailingHarmonie]

The external water temperature will have no effect on the engine’s internal temperature which is controlled by a thermostat. You have changed the switch, and that would be the easy first try thing. Do you know the pressure rating of the switch you installed?

I assume this is happening while the engine is running at speed, that would be an unusual time to see a marginal oil pressure.

Has this engine ever overheated? Does it consume any oil? Does it leak oil? How many hours on the engine? If it’s a MasterVolt branded generator, we know it’s not new…

Others might have an better idea, but it seems like it’s time to get a gauge in-line to measure what the pressure really is. If it REALLY is low enough to trip the switch while at normal operating speed, that’s likely symptomatic of a serious issue with the oil pump, seals, or bearings.

[skipperpete]

I have no hands on experience with that particular Mastervolt 2 pole generator and a web search disclosed that it’s an oil cooled engine, apparently a Kubota engine is used in this particular model (3.5- 3500). I don’t know how this oil cooling is accomplished, it could be by water cooled heat exchanger or by an air cooled radiator (which would make little sense with a sound shell housing in a yacht engine room) but the fact that opening the shell changed the shutdown interval might somehow be linked to the oil cooling. I’ll do a bit of research, I’m curious about this departure from mastervolts conventional raw water/coolant system[ATTACH]

[davethedog]

Thanks for the advice and be good to get this sorted, but as said I have just ran it for over 2 hours with the shell off and the engine bay open and it was fine!

Strange indeed and appreciate the help.

[GreenWave]

Assume it has a separate temperature sensor/alarm? Is that just an idiot light or is there a reading you can get?

[skipperpete]

I did a bit of browsing during smoko to learn more about your genset and if it’s powered by the Kubota OC 60 or OC95, it does indeed have an oil cooled head, an oil cooler and an air cooled cylinder. I would have thought that any type of air cooling in a yacht would render below decks barely habitable unless you cruise the high latitudes but if this your engine it theoretically suggests a lube oil viscosity problem that’s creating the low lube oil pressure shutdown. The workshop manual for that engine asks for SAE 10W-30, 10W-40 or just SAE 20 to be used in 0°to 25°C so possibly the viscosity is too low when at operating temp and the oil pressure drops accordingly.... or the little finned radiator type oil cooler is blocked. All this rambling is me trying to figure out why the engine runs fine with the sound shield open and not so much with er boxed in.
If this is not the engine in your genset, ignore this post [emoji848]

[davethedog]

Update on this:

I have changed the oil again and, fingers crossed, has been running a lot better.

Time will tell as perhaps the oil was a bit contaminated, so I have also changed the oil today as a pre-emptive measure!

[skipperpete]

Thanks for the update, I hope it fixes the problem. If the engine is the Kubota OC, I’m wondering ....where does the heated air go after cooling the cylinder and engine oil? Is the sound shell vented to outside of the hull/engine room or does it simply consume the heated air via the engine intake.
Pete.

[davethedog]

The shell is no vented, so no idea!

As for is it fixed...we will see!