5.7 GM only runs at 120 degrees

[ringmaster72]

I just got my boat last year and put a new motor in it and it never got hotter than about 120-130 degrees. I changed the T-Stat last year but it still never ran any hotter. Any ideas on why it does not run hotter? No matter what I was towing or what speed it went it never got warmer than that. Oh and I also changed the water temp gauge just to make sure it was right.

 

[rbh]

Re: 5.7 GM only runs at 120 degrees

hey there
when you put the new gauge in was it compatible with the sender (electric only)
you can always test it with a a mechanical style.
rob

 

[Rocky_Road]

Re: 5.7 GM only runs at 120 degrees

You might have been able to reuse your old sender unit, as well as your original guage. You already know that they were compatible.

That way you would have something to compare your old running temperatures to.

 

[180shabah]

Re: 5.7 GM only runs at 120 degrees

t-stat and gauge replaced, what about the sender?

Have you checked the temp with either a machanical gauge or an IR thermometer.

 

[sdoomaha]

Re: 5.7 GM only runs at 120 degrees

May be out in left field, but you may want to check your thermostat again. I have a 4.3 (5.7s little brother) but if the coolant system is the same, the coolant circulating in the engine may never be getting to the temp sending unit.

On mine the thermostat wouldn't open....and the temp sending unit was in the thermostat housing on the "cold" side of the thermostat. It would heat up to 100-120 but that was just the heat from the engine being transferred through the metal. Tested the sending unit, tested the guage, then tore apart the thermostat housing and realized none of the coolant circulating the engine was ever getting out. Luckily I had not been running my boat hard this Spring so I didn't cook anything. Replaced the thermostat and all is well. Heats up to 160 and stays there. Might want to check the manual to see if your thermo housing is the same....might be something else to take a look at?
If it's different...sorry for sending you on a goose chase.