Operating Temp of a 5.7 Mercruiser ?

[johnebquick]

After rewiring and doing a lot of restructuring in the motor, I'm not sure if the water
temp is operating properly.

What is the average operating temp of the merc 5.7L?

I'm not going over 145 deg. I'm thinking the thermostat was removed or is it just working
that well? Could this be the correct temp? I know when I was tubing with the kids and
I kept running it and then turning it off and drifting until the next set, it might creep up to
maybe 175-180 deg but never higher. If this is correct then WoW ! I'm not used to motors
running this cool. If not then maybe I need to replace my temp sensor. I guess I could
test it in a pot of water on the stove with an additional stat to verify.

Thanks,

John

[Judith A]

John if the engine is raw water cooled 145 would be about right. if fresh water cooled usually run up around 175

Mark

[Innovator]

John,

I'm guessing your heat exchanger is shot, like mark said if it is fresh water cooled it should run at 175, your running at 145 essentially the fresh water cooled engine is runnning as a raw water cooled engine b/c the heat exchanger is allowing crossover between the coolant and raw water. I this happen on an old mercruiser of mine

Kevin

[johnebquick]

I forgot to mention that it was raw water cooled. I take it then it's OK? I'm not sure about the heat exchanger though???

[Innovator]

If its Raw water cooled you don't have to worry about the heat exchanger, because it does not have one.

[fishfighter]

Raw water cooled is 145F. That can change due to water temp that is coming into the motor/ winter time. Close water cooled and if it is an older engine(pre vortec ) running temp is set at 155F. Newer mercruisers should be closer to 175F.