1982 40hp Merc Overheating

[davebad22]

Recent purchase so I don't have a lot of history. Noticed it over heating when last operated. Saw water coming out around upper spark plug. Replaced gasket and no more leak. (also spark plugs)
Ran the engine (low idle) for 10-15 min with hose hooked up via a flush device. Started to overheat. Stream of water was coming out the pee hole at the time.
First question, If the impeller is shot will the preasure of the garden hose force water out the pee hole when the engine is running?
Next- what other test should I perform to pinpoint the problem and in what order.
thermostat? Impeller ? or....?
Any other comments or help?

Thanks, Dave

 

[Laddies]

Re: 1982 40hp Merc Overheating

Yes, pressure water will bypass a bad impeller and the engine does have a thermostat

 

[davebad22]

Re: 1982 40hp Merc Overheating

Ran the motor while submersed in water tub. Still had stream coming out pee hole and still got hot.
Apprx. how long whould it take for the outboard to get hot if the thermostat is not working properly?

Thanks, Dave

 

[Laddies]

Re: 1982 40hp Merc Overheating

If you have no water at the telltale then the impeller is bad and sometimes if a engine is overheated it will also ruin the thermostat

 

[davebad22]

Re: 1982 40hp Merc Overheating

Took thermostat out and did test. Seemed to open up around 160 degrees but is it possible that it could have been stuck while it was in the engine?

 

[davebad22]

Re: 1982 40hp Merc Overheating

Just checked out impeller. Only had about 1 1/4 out of 6 blades left on it. Also found 2 pieces stuck in the water outlet tube blocking flow.

Just order impeller, thermostat and gaskets. Hoping for a happy ending.
Thanks to those who replied,
Dave