Overheating 1992 Pro60

[fenwick]

I am baffled,I have a 1992 Pro60 that overheats at idle or trolling.I have replaced the impeller,checked the housing(not warped or melted).I have checked the thermostat on the stove and it opens when it is supposed to.I have even taken the thermostat out and run the motor and it still goes into the SLOW mode till it cools down enough then it runs like a top.At mid range and WOT there is no overheating.The tell tale stream is not to forcefull at idle,it seems a little weak,as you increase the RPMs. it gets stronger.I took compressed air and blew up threw the water tube, I got air out threw the thermostat opening but it wasn't to forceful.Should a good amount of air come out of there? Also, what is that threaded plug right next to the thermostat housing? Is that used for flushing the motor? If so what would a person use to back flush a motor and how would you go about it? I am getting really frustrated.Any input would be greatly appreciated!!


Fenwick

 

[Swe-Bayliner-89]

Re: Overheating 1992 Pro60

They usually don't recommend blwing air into the watertube because you risk damaging gaskets.
I think the risk is small though.
A wire or something is the usual recommendation.
If you only blew it up the air tube you may still have clogged up cooling channels around the cylinders.

I think gaskets under the cylinder top is what you might want to look at next.
It might be that on idle some of the cooling water may leak into the cylinders, and when you open the throttle it's being pushed in the cooling channels.

Can't really think of any other explanation to your problem, but keep in mind I'm just guessing here.

 

[fenwick]

Re: Overheating 1992 Pro60

Swe,

Thanks for the reply,but it is still overheating.I checked the thermostat again and I'm a little confused on when it should start to open and at what temp. it should be fully opened. On the back of it, it is stamped 50 C. When I tested it again it only began to open at 55 C., and was fully opened @76 C. Is this correct or should it be fully opened @ 50 C.

Fenwick