Closed Cooling

[rugbyscorp]

My brother has an 87 sun ray with a merc 170 with a closed cooling system. It is running about 200 d f. is this normal? If not where should we start looking for the problem?

 

[Don S]

Re: Closed Cooling

No, it's not normal. First place to look for overheating on any marine engine is the raw water pump impeller. They should be replaced every couple of years as a preventive maintenance item.

 

[rugbyscorp]

Re: Closed Cooling

We changed the impeller on the drive unit, where is the raw water pump impeller located? On the engine.

 

[roscoe1]

Re: Closed Cooling

I have a 1977 Formula that was running alittle warm even after replacing engine water pump, thermostat, sending unit, and raw water impellar. Turned out to be the intake hose from the thru-hull to the raw water pump was old and became soft thus kinking the hose and restricting water flow. Replaced with new hose and it runs where it should.<br /><br />The raw water pump on my boat is a belt driven pump located at the starboard side front of engine with a curved hose that picks up water through bottom of hull.