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1977 johnson seahorse 6hp

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backwoodslivin

New member
Hello,

I bought a used 1977 6hp johnson seahorse and to my delight the cooling system was plugged. I did run the motor repeatedly to the point of overheating.

Does this motor shut off on purpose? Is there some kind of over heating kill switch. I wonder if the motor is garbage? Did the overheating damage piston and cylinder?

Thanks!

Adam
 
There is no overheat shutdown feature on this motor.----Do a compression test and post the actual numbers here.----Maybe you are lucky.------New style head gaskets are better than the factory originals.------If compression is good take head off and install new gasket.-
 
There is definitely no overheat feature to turn the motor off. A buddy of mine gave me one that was overheated to the point of locking up. TWICE!!!! I never did a thing to this motor, and it still runs fine today... They seem to be pretty tough motors..

If able to, pop the heads off. you will probably find the source of the clogged cooling system and can take a look at the cylinders. I am sure that you probably didn't do it any favors, but there is a very good chance you didnt do any serous damage either
 
When you put it back together, the head is probably warped. Deck it by using a sheet of 100 grit waterproof automotive sandpaper, laid on a sheet of glass. Just use some soapy water for lube.
I trace around the head with a permanent Sharpie…when the sharpie marks are all gone, it is perfectly flat.
I bought an 8HP a couple years ago that showed quite low compression. It had been overheated to the point of melting a plastic throttle linkage. The head was warped over 5 thou. After decking & a new gasket from Racer that motor ran as good as new.
Here is the thread-

8HP Johnson 1991 J8REIA Fixable or break up for parts?

I have a smooth running ‘94 Evinrude 8Hp, but have been on the lookout for a spare prop. I came across a farmer who had tossed this ‘91 Johnson 8HP in the scrap pile. Said he lost the water pump & overheated. Sat in his shop for a couple years, his kid went to look at it & said it was seized, so...
www.marineengine.com
 
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