PQ290Enticer

I have become "obsessed" with the oil temp. I am constantly looking at it and it's starting to mess with the "fun factor" of boating for me. I am using these oil thermostats from Improved Racing. FSM-215 that are factory set at 215 degrees. I was thinking these would allow (force?) the oil to reach the 215 degrees and then regulate it at least close to that number provided the oil cooler is sized correctly. If I am idling the temp is less than 210. When cruising it is just shy of 230 degrees. When WOT it goes somewhere between 230 and 320. (That's the spread on the gauge) Are you guys experiencing the same thing or is your thermostat keeping the oil temp stable? This really makes me wonder what the oil temp was when everything was stock from Mercury? I have a feeling that the oil temp went way up because when I tore the engines down there was the distinct smell of burnt oil. Could just be the 780 hours of use too I suppose. I'm thinking about bypassing the thermostat and see what happens. Any thoughts on bypassing the thermostat? Thanks for your input.

DrFeelgood

Thermostat sets the minimum temperature before going to the cooler. It does nothing for any temperature above the thermostat set temp.

Once the thermostat is open, it's open. There's no control of how hot the oil can get, only how cool it can get. Larger oil cooler or addressing water flow issues through existing cooler would be needed if you truly have a high oil temp situation. Or address any internal issues with motor creating more friction and higher oil temps.

Rookie

iTrader: (4)

I'd remove that contraption and run it. If cooler keeps up then you know what problem is. I don't believe that is flowing enough oil to the cooler. Probably just bypassing the cooler.
320°F is way too hot IMO.

compedgemarine

I deal with this all the time in the old cars. thermostats do not make things colder. they just allow for cooling after their set point. if something is running 210 degrees with a 190 thermostat then going to a 160 will not make it cooler because there is not enough cooling effect in place. in other words the cooling device, radiator, heat exchanger, etc. cannot shed heat fast enough to bring it down to the temp the thermostat would start to close. you either dont have enough cooler or the flow is restricted such that the cooler cannot move enough thru it.

KWright

If I remember correctly your bearing clearances were on the tight side. That could be a cause. If oil temps were in the 320 range I would definitely cut the oil filter apart and check for bearing material. We run 220 deg. Thermostats also piston oilers and spring oilers and have no problem holding temps at 230.

compedgemarine

KWright, what are you running for coolers? bellhousing or tube? the race boats always ran around 230 running hard and would drop to 210 or so pretty quick when you slowed up. we ran bellhousing coolers which as I understand it are quite a bit more efficient than the tube style.

PQ290Enticer

Thanks Doc for your comment. I was not thinking it through correctly. What you said makes perfect sense.
Rookie, I am going to order the couplers to bypass the thermostat and see what happens. In my top speed run vid it didn't make 320 but was between the 230 and 320. As I get more hours on the engines it may settle down??
compedgemarine, Your post is along the lines with DrFeelgood. I am using a 3"x23" tube cooler. It also cools the power steering fluid. It was supposed to work on engines up to 700 hp so I thought I had some "head room". I was wondering if I had a blockage somewhere but it's in both engines so that seems less likely?
KWright, Yes the clearances are closer than anyone on this site would use. I have less than 10 hours on the engines aside from dyno time. I suppose they will take a little more time to properly be broken in? I will drop the oil at 20 hours and cut the filter apart.
Very early on I was told to get an oil thermostat because with the oversized cooler and running in the cold water of Lake Michigan that I may have a hard time getting any heat in the oil. It just caught me off guard that it runs hot. I really thought it would be locked in at 215 degrees again thinking this worked like a water thermostat in a car. There is plenty of water running through because at cruise or WOT the water temp drops a lot. Probably from idle which is very close to the 160 degree thermostat I'm using down to maybe 120 degrees running at cruise etc.
Thanks for all of your comments and help.

SB

iTrader: (1)

Tune, believe it or not, can greatly effect oil temps too.
i haven't read thread thoroughly so not sure what’s been discussed. I’m beat abd food cons’ing…lol

KWright

we run bell housing coolers both are 15 plate. Running the spring oilers puts alot of heat into the oil. We also have a drain back hose from back of cylinder head to the pan.

underpsi68

I would cut the filters open now just to be safe.