1987 85 hp force overheating problem

[marky mark]

hi am working on 1987 85 hp force ,the top end is all new ,i changed the complete water pump system in the lower unit ,when the boat gets on plane i can go about 3 to 4 hundred yards then the buzzer goes off an the water coming out the back is really hot ,then u let it sit for about 5 minutes ,then start it up an go the same thing happens ,i took off the bleeder screw at the top of the motor an started it there is alot of water there ,could there be a problem with the thermas stat ,or could the timing be off making it run hot ,an if so how can i check it .Cause this motor is driving me crazy ,so if anyone has any info that would be great thank u for your time

 

[CharlieB]

Re: 1987 85 hp force overheating problem

Test the t-stat in a pan of hot water with a thermometer. Full open by 140

 

[marky mark]

Re: 1987 85 hp force overheating problem

but would water still come out the rear of the motor ,if the t-stat was closed

 

[marky mark]

Re: 1987 85 hp force overheating problem

Test the t-stat in a pan of hot water with a thermometer. Full open by 140

but would water still come out the rear of the motor if the t-stat was closed

 

[maxum247]

Re: 1987 85 hp force overheating problem

I put my boat in the water and start the engine, let it run about 1000 rpm in neutral and within seconds the releif holes start spitting water! If you watch the stream from the time the engine first starts you'll notice the spray from the releif holes increasing as the thermostat opens and the engine reaches operating temperature. My guess is that some water does get by the thermostat.
The thermostat can get partially blocked with debree and allow some water thru but not enough to cool the engine completely causing the water to steam.
Other problems that can be present are the passage way's in the engine block could be partially blocked by a pebble or corrosion. The strainers on either side of the lower unit gearcase behind the propeller can get partially plugged up at times. Any of these conditions in my opinion would be reason enough for the buzzer to keep sounding.
Do the test prescribed earlier and see if the stat opens at the temperature stamped on the end of it! If so it's good, if not time to replace it! max!