Mercruiser operating temp

[Mike_Maranto]

What is normal operating temperature for RWC mercruiser 5.0 year 1994. Mine runs at low rpm around 150/160 on high speed 175/185.... Is this normal?

 

[Bondo]

Re: Mercruiser operating temp

Ayuh,... Sounds about right...

 

[c03camson]

Re: Mercruiser operating temp

Its normal for a 160 degree thermostat engine to run 175-180??

 

[mjgates]

Re: Mercruiser operating temp

I have a 5.0 Merc that runs between 165 and 170

 

[Mike_Maranto]

Re: Mercruiser operating temp

Its normal for a 160 degree thermostat engine to run 175-180??

c03Camson I have 140F thermostat from the merc dealer.

 

[Don S]

Re: Mercruiser operating temp

c03Camson I have 140F thermostat from the merc dealer.

Then you shouldn't be seeing any kind of temps over 170? When was the last time the impeller was replaced?
Even a temp of 185 on a raw water cooled engine with a 160? stat is to high.

 

[c03camson]

Re: Mercruiser operating temp

My stat is a 160 (2003 merc 5.0mpi) and it has always run at 160 but when i changed the impeller it started running about 175 so im gonna check it this weekend and change it. thought it was my circ pump and/or thermostat but they are working normal.

 

[Mike_Maranto]

Re: Mercruiser operating temp

Then you shouldn't be seeing any kind of temps over 170? When was the last time the impeller was replaced?
Even a temp of 185 on a raw water cooled engine with a 160? stat is to high.

Impeller was changed this April, manifold, riser, circular pump t stat at the end of April

 

[madurodave]

Re: Mercruiser operating temp

This bothered me for months. Until i used a temp gun and found that my gauge was off by 20 degrees or so.

 

[Mike_Maranto]

Re: Mercruiser operating temp

This bothered me for months. Until i used a temp gun and found that my gauge was off by 20 degrees or so.

I got the temp gun, where should I point it, at the temp sensor???

 

[Bondo]

Re: Mercruiser operating temp

I got the temp gun, where should I point it, at the temp sensor???

Ayuh,... At the intake manifold, at the base of the T-stat housing...

 

[netting one]

Re: Mercruiser operating temp

maybe a dumb guestion but do you have to run a thermostat at all?

 

[c03camson]

Re: Mercruiser operating temp

If that impeller was installed with the fins going in the opposite direction would it still work? and for how long?

 

[Don S]

Re: Mercruiser operating temp

netting one & c03camson, if you have questions, please start your own thread and ask. Don't hijack Mikes thread.

 

[Bondo]

Re: Mercruiser operating temp

maybe a dumb guestion but do you have to run a thermostat at all?

Naw,... Not unless ya want it to run Right....

 

[freak007]

Re: Mercruiser operating temp

A thermostat controls MINIMUM operating temp. Max temp is controlled by the rest of the cooling system. Operating temps below 165*F greatly increase engine wear. Oil temps are typically 20 to 35 degrees hotter than coolant temps, and you want the oil to get hot enough to boil out any condensation. Engine temps in the 180* to 190* range would not concern me at all. Higher coolant temps also vaporize the fuel better preventing plugs from fouling, and reduces fuel consumption and emissions.


Running without a thermostat is not a good idea. Not only can you "overcool" your engine (resulting in condensation in the oil and increased wear), you can actually create an OVERHEATING condition that would never be detected on your gauge.