1987 85 hp force overheating

[luckyman1]

ok,i pulled l.u. checked impeller, and pump ,both appeared fine.reassembled,no water getting to thermostat.alarm sounded shut off.intake below appears clear,does it need to be in gear to engage impeller or does it still pump in nuetral?I feel like an idiot here but i am stumped.also,Frank your intructions were right on thanks.

 

[pnwboat]

Re: 1987 85 hp force overheating

If the engine is running, the water pump should be pumping water regardless if it's in neutral or in gear. A bad impeller sometimes does not look that much different from a good one. I think it has more to do with the flexibility of the rubber vanes on the impeller. If you're using a hose with muffs, it's often hard to get enough water flow to the motor due to alignment issues with the water outlet on the muffs and the water intake on the motor, or low water pressure. Putting the lower unit in a tank or some type of container that will allow you to submerge the lower unit well above the cavitation plate is the best way.

If you don't think you have a water flow/supply problem to the lower unit, change the impeller and test again.

There is a possibility that you might have a blockage in the water passage between the water pump and the thermostat, but first eliminate the water pump itself. To trouble-shoot the water flow between the pump and thermostat requires more time, money for gaskets, and the possibility of creating other problems.

 

[Jiggz]

Re: 1987 85 hp force overheating

Remove the LU again and put it aside for now. Remove the t-stat and replace the cover. Get a garden hose and open the spigot just enough to get water pressure and hold it against the water tube where the impeller housing connects to the LU. You should see water coming out of the exhaust snout. If none, increase the pressure a little bit and hold tightly on the hose against the water tube, if still no water out of the exhaust you have a blockage somewhere.

However, if there is water out of the exhaust snout, double check the impeller and make sure when you put the LU back the water tube is inserted with the impeller housing outlet. The impeller should not have signs of cracked or permanently deformed fins or worse yet missing fins. If after re-installing the LU and the problem persists, remove the t-stat and try again.

 

[jerryjerry05]

Re: 1987 85 hp force overheating

Welcome.
The muffs on right?
Duct tape.
In a bucket?
Water needs to be 2-3 inches over the cavitation plate.
Like Jiggz suggests remove the lower and apply the hose direct to the pickup tube.
If the thermo's been removed? the water should come out the thermo hole.
Test the thermo in hot water.

 

[MickLovin]

Re: 1987 85 hp force overheating

For the cost of it get a new thermo, gasket and impeller, least you will have peace of mind that they won't need changing for a season or two, and with the thermo you shouldn't have to change it that often anyway. Also as soon as you start playing around with the thermostat, you will in most cases need a gasket due to the old one tearing in most cases, unless it has been done recenlt and the gasket is fairly new. I have had the same problem and did what Jiggz has suggested, this flushed out some sand which had been caught in the cooling system, probably from being beached with the motor in the sand and running (75HP Chrysler). I also found later that the previous owner had also put the thermostat in reverse, so when I was at WOT or just below, my buzzer would go off. I bought a new thermo and replaced the impeller, flushed the water tube and it was fine after that, all this didn't take that long as I had bought the parts already as part of my new to me engine maintenance.
Also I never put my motors on muffs, don't trust them never will, I even have the original chrysler ones which I will put in a museum one day as never been used LOL.