ENGINE RUNS COLD 5.7 Merc

[ddecoursey]

Hello,


I have tested gauge /wire = OK
bought new sending unit guage still reads C needle never moves

Bought laser temp tester, ran engine for 20 min increasing the rpms from time to time during test and was hard pressed to getthe infared gizmo to get past 100 most times the sending unit and thermostate housing was in the high 90's riser on exhaust was up to like 105 degrees hoses did not feel hot

anyone ableto speculate where this is taking me ??? I'm not brave enough to just go out and zoom around

thanks

 

[mkast]

Re: ENGINE RUNS COLD 5.7 Merc

Change the thermostat.

 

[snoski]

Re: ENGINE RUNS COLD 5.7 Merc

Your thermostat is stuck in the open position. Replace with a new one...

 

[MikDee]

Re: ENGINE RUNS COLD 5.7 Merc

You can't judge the engine temp off the garden hose. Take it out on the water, it'll get up to operating temp, thermostat or not! If it's raw water cooled it should be a 142* thermostat, which sometimes won't even raise the gauge idling on muffs. If it's closed cooling the thermostat should be a 180* unit. I've even run mine on occasion without a thermostat, no problem, but it takes longer to reach oper. temp. A cooler running engine, has a denser fuel charge delivering more power, that's why racers use 142* thermostats. If cold running bothers you, replace your thermostat, it's probably stuck open, one more good thing, the cooler your engine runs, the higher the oil pressure, but it's not as fuel efficient, or as good for emissions, if you care