Running 2 540s 650 hp with no blowers on a Cigarette Cafe Racer 1993.

Seawater cooled system (not closed) CMI dry exhaust

Sea water temp around 86F at present

Oil temp at 4000 rpm around 215-225 F

Water temp is only around 100F or just above @ 15-20 psi water pressure

I have 2 water intake in the hull that can be open separately apart from drive suction. Im running with them open. Have not checked if water temp will increase if they are closed. Maybe it will drop little as the drive suction will not reach same 20 psi pressure.


New impellers 40 hours ago, last year.

I cant see any thermostat as i assume it will be on the engines on the fwd side housing?

as i understand if i get increased water temp my oil temp will also increase?

However the question is if this 100F is too cold or not? if yes what problems does it cause the engine?

Another thing iv noticed is that during idle my oil pressure is around 50 psi ( 65-70 cold) but it drops during running to 35-40 psi, is that too low? Local reading is around 40 and dash reading is 25-30 psi. Oil and filter 40 hours, will check what spec the oil is.

Henrik

How does your oil look?
Cold temperature can condensate your oil.

Oil looks like new, just slightly darker but transparent on the dip stick

How big is your oil pan? Oil line size? Cooler size? Fitting size at block and cooler? What filter are you running? What brand and weight oil? I don't think your motor will live as long as it should at that pressure running... You need to take the filters off and cut them open. Also is there alot of 90's in the oil system?

oil temp seems fine to me if i compare to anothet 650 boat i ran

If you're only seeing 100* water temp there's no way there's thermostats in those engines. The waters a lot colder here (like 50*) and my gauges won't even register. Your oil temp seems high though. Im usually between 160-180. My oil pressure is 80ish cold idle, 65ish running and 40ish warm idle. I've always been told 1# per 100rpm is more than sufficient. Obviously 10#s at idle is not ideal but its supposedly enough to not cause damage

full synthetic 25-40 and mercury racing performance filters. Dont know oil amount as it was changed by shop. Just realized that my local gauge is before filter and remote gauge is after filter.

If the filter is dirty it explains the pressure drop from 40 to 25-30 but why does it not show when cold?

ill change filters before next run.

there are no thermostats , boat has been running in Ozarks for the last 7 years before i shipped it over here.

Idea? Most factory raw water cooled performance boats come with 140-160º thermostats.
I'd be tempted to try a 140º thermostat and see if the boat performs better.

I would think if you were to increase your water temp 40º you will see a climb in oil temps.
According to the chart an oil temp close to 200º seems to be best for bearings. I don't know
if I would spend my $$$s on bigger coolers unless your oil temps climb considerably higher as you increase
R.P.M.s over 4000.
Hopefully one of the expert engine builders will give their opinion.

I think your temps are great.

imo if your oil temp does not go higher at wot you are good to go.if you run hard for long periods of time id try a good quality 20w50 oil and see if anything changes.