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454 Mercruiser .. Operating Temp

ehlien

ehlien

Regular Contributor
What should the normal operating temperature be?
Will the operating temp be the same when on muffs and a hose??
How long can you operate the engine on muffs?
 
What should the normal operating temperature be? depends on the thermostst but most are 160
Will the operating temp be the same when on muffs and a hose?? The hose connects to the muffs????????????
How long can you operate the engine on muffs? With constant water, untill the gas runs out
 
Raw water cooled engines have 140 ish degree t'stats and run pretty near that temp, if boat has a heat exchanger it usually has a 160 ish t'stat and again will run about 170 ish... You can't load up an engine on the muffs, so the temp you see on muffs ( assuming good flow and no aeration) will usually be just at or possibly below the t'stat rating. Running engine much above idle on muffs for more than a very brief blip, not a good idea.
 
Just changed out the sea water pump. Not sure what the thermostat is but I ran it with muffs for about 10 minutes and know it heats up over 160. It does not have a heat ex-changer. Will put in a new thermostat tomorrow. I have heard of people that run without any thermostat.
 
ehlien said:
Just changed out the sea water pump. Not sure what the thermostat is but I ran it with muffs for about 10 minutes and know it heats up over 160. It does not have a heat ex-changer. Will put in a new thermostat tomorrow. I have heard of people that run without any thermostat.
Click to expand...

No T'stat, yes and folks don't use seat belts also. Purpose of T'stat is to insure that the engine gets WARM enough. not keep it cool. Running a boat without a T'stat abuses the engine the same as if you ran a loaded truck in the dead of winter in below freezing weather before the engine warmed up a long continuous grade.

If you run exclusively in fresh water bodies of water (or if you have a heat exchanger), then the 160ish T'stat is the correct one. Direct sea water cooled in salt or very brackish water should be a 140 ish t'stat.
 
Thanks for the feedback. Think I will try to split the difference and look for a 150 T stat. I think a little cool is better than a little hot.
 
Again... do you run in fresh water or salt??? From your "location", I might assume fresh, but please confirm.
Running a t'stat over 140ish in salt ( or brackish) water leads to problems.
The reason folks run 160s in fresh water is to get better fuel efficiency and fewer engine problems ( lube system is happier at the higher system). With a cooling system in good health, hotter is better.
 
What is "running good temp wise" mean

One of your other posts you say 100*.............that is no good.

You must be between 150 and 170 depending on thermostat. It does not matter if you are on a hose or in the water the thermostat will maintain the same temp when not under load.

Because of all your posts always include the basic information in each new one, Year, engine size, and serial number if possible so if you ask a question the correct service manual can be used. You are not the only one asking questions.
 
1994 Baja 272 with a 454 Mercruiser ..350 hp and Bravo 1 .. running temp with 160 thermostat is now right at or about 160 at 2500-3000 rpm in the water . Thanks much !
 
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