raw water cooling - cold water - engine temp?

[rbryn]

The water around here has dropped to a chilly 58 degrees and we've started noticing that our engine temp is fluctuating a lot more. Not sure if I have a thermostat stuck open or if this is normal when the water cools down.

When at idle, the engine temp drops to about 145. At speed (anything above 3000 rpms) it hangs at 170. as soon as we slow down below 2000 rpm's it drops back to 145 again.

I'm used to it just hanging at one temp, not this flailing about back and forth. The engine is raw water cooled - figured it the thermostat was stuck open, i'de see alot cooler running temp all the time, not this on/off again temp changes.

thanks

 

[Woody]

I think you have a thermostat or guage problem. I have run in mid 30 degree water and never had my temp fuctuate like that.

 

[nickysc]

Sounds like the thermostat is failing.Itsnot hard to change. The cooler water temp makes the engine cool downquicklywhen the rpms are lowered.

 

[JeffMendenhall]

I would think you have a thermostat stuck partially open. It should control your engine temp regardless of water temp. It should close if the temp is dropping so the engine temp stays constant. You may have something stuck in there keeping it from closing all of the way.

 

[osd9]

I think you should ask the new member Happy Times....I'll bet he has the answer.

 

[Quint4]

Possibly impeller ? I would check (.... on your motor with a Bravo).

 

[rbryn]

Possibly impeller ? I would check (.... on your motor with a Bravo).

We just had the impeller changed about 15hrs back (preventative maintenance). But, it's possible something got by the impeller and hung the thermostat open.


Thanks everyone for the quick replies. figured it was the thermostat but needed the confirmation

 

[Hampton]

Thermostat is on top, center of the engine facing the front of the boat. It requires 4 bolts to access. Be sure to get the right MARINE thermostat for your engine and a new gasket. If you haven't done this, clean both surfaces before re-installing, but don't use a tool that may gouge the surfaces when trying to remove the old gasket. Take note of which way is up when removing the old one.