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Engine Temperature

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Standard thermostat in my 340 Monsoon holds engine at 160 degrees F. Lots of talk about how this is too cold and unhealthy for a fine American V8 engine, requires blowing carbine out with a hard run at day's end, and generally causes angst within the motorhead community.

Question: why not switch thermostat to a higher temperature model? I'm personally not concerned about boiling fish, since they can't swim fast enough to keep up with me in the first place. If it will make my Monsoon feel better, I'm all for it.

So, is this something one should consider doing, or are there reasons (other than boiled fish) that it should not be attempted?

Enquiring Minds want to know....

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Umm, running in an enclosed compartment maybe? The thermostats used to be 140° but they upped them, perhaps to provide better warmth for boats equipped with heaters, IIRC.

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My version of the 365 hp Hammerhead is known for collecting excess gasoline in the crankcase oil. An Indmar service bulletin suggested running the boat for a 15 minute lake run at 3500 rpm to raise the engine and oil temp enough to evaporate the excess fuel from the oil. Following that procedure did not eliminate my fuel in the oil problem.

An Indmar factory tech suggested that I install a 180 degree thermostat in my 365 Hammerhead. The extra temp would help for better piston ring expansion. I was concerned that the extra temp would create problems with the rubber exhaust elbows. The Indmar tech assured me that would not be a problem, and that you could use up to 190 degree. My engine runs much better at 180. With the 160 thermostat sometimes it would stumble on takeoff and felt like it was backfiring. It has not done that at all with the 180 thermostat. It idles smoother, and does not leave as much black soot on the transom. I have not changed my oil yet so I can't say if that helped to reduce the excess fuel in the oil.

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Thanks for the input, BillFooter. Very helpful. I'm definitely going to discuss running mine at 180 temp with Indmar. I've seen other comments that implied the 160 temp was for ecological reasons, not performance.

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My understanding was that certain waters had elements that could cause seperation and due internal damage to the casting and not anything to do with the temp to the enviroment, and I would have to say if your engine ran better at the higher temp than indmars calibrations of the soft ware was incorrect for the 160 stat, for all advance curves and fuel injector fireings are based on temp. In general most computor strategys are based on temp going from cold to hot.

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Your ECM software (load curves) is no doubt written to run at 160*, but like Bill said, a warmer engine is going to run smoother. Personally, I don't think running a 180* will hurt anything. Your exhaust manifold might run a bit warmer too, being 180* water will now run into them, but this water is constantly mixed with raw water anyway. I think the 160* stat is there for salt water use, which must be kept under 170*, and a larger margin of safety for potential overheat problems. The 180 temps do put you closer to the limp mode temp, which is 203*.

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Here is Indmar's reply:

The engine was built with a 160 and that is what it should have. There is a Coast Guard regulation that nothing in the engine compartment can be over 200 degrees. We can stay in compliance using a 160 thermostat but a 180 could put us out of compliance. The engine would probably like running a little warmer but we can’t let it get too warm and stay in compliance.

Larry Engelbert

Indmar Marine Engines

Power to the Sport

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This thread makes me feel totally under educated as a boat owner. (i should have misspelled something there, it would have been funny). BUT SERIOUSLY (and not to hijack the thread) but how/where can I become more educated when it comes to my boat? I thought I knew the basics, but.......Well, lets put it this way: There is no way in H&LL i could point out the crank case or piston ring! (I might have a shot at the 'rubber exhaust elbows'.)

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If you don't do your own mechanical work, then why waste your time? We're on here as a collective group of amateur mechanics for the most part, sharing a love of machinery, boating, and grease under our finger nails on Monday mornings.

Like a guy told me when I was in high school working at a gas station, if don't know how to change the spark plugs on a diesel, you better not be working on my ride.

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If you're really not comfortable around engines due to lack of knowledge, don't feel bad. But, also, don't feel the need to "get to know" your boat, if you don't need to, leave it alone or to the professionals. There's a lot of professionals on this board.

edit...you could get started at learning something by downloading the linked PDF in my signature on winterizing your boat, just a thought.

Edited by Pistol Pete
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