1984 Johnson 15 HP overheating

bruceblaisdell

Recruit
Joined
Jun 27, 2011
Messages
2
HELP, I replaced the waterpump, thermostat, spark plugs before using this motor. We took it out yesterday, ran GREAT for 10 minutes, was peeing good at first, then we heard a low squealing noise and then peeing water turned intermitant. I headed back but motor shutoff and was VERY HOT and frozen. We got it back, and after it cooled down became unfrozen, we started it on ear muffs, and did not pump water (I didn't have a tank to run in). Took off lower unit, and water pump looked fine. I took off peeing tube and blew in while holding intake tube (from water pump) to see if there was a clog. CRAZY, when I blew in peeing hole tube while holding thumb on intake tube from water pump, was easier to blew in then while not blocking intake tube (you would think it would be the other way around easier to blow in while not blocking intake tube). Can anyone help?
Forgot to mention, we pulled the sparks plugs (no water and looked fine)
 
Last edited:

fireman57

Captain
Joined
Aug 24, 2004
Messages
3,811
Re: 1984 Johnson 15 HP overheating

Muffs are not good to check water pump with. If you have a trash can put it in it and make sure you have water halfway up the midsection and test again. DO NOT rev in neutral. If it doesn't pump then you have a blockage or possibly a bad thermostat.
 

Monte1961

Lieutenant Junior Grade
Joined
May 8, 2011
Messages
1,180
Re: 1984 Johnson 15 HP overheating

Get yourself a clean trash can. And as fireman said, fill it above mid section. Impellers are not self priming. Start engine and count ten seconds. Is water coming out peepee tube? (NO) Remover thermostat, replace housing temporally, start engine. Is it pumping? (NO) Remove lower unit and rig garden hose to fit water tube. Turn water on. Is water coming out now? (NO) Blockage in water passages. Will have to remove head and blockage. If water is coming out, Lower unit has blockage. Check water intake and passages, check impeller housing for damages. Post back results. Welcome to iboats.
 

ultra353

Petty Officer 1st Class
Joined
Jun 21, 2009
Messages
387
Re: 1984 Johnson 15 HP overheating

Also make sure the impeller key is lined up in the keyway for the impeller. That noisie you heard could have been the key grinding against the metal in the impeller hub if it was not in the keyway, it pumped for a bit while at low rpm`s but eventually the key broke or came out. Just something else to look at.
 

bruceblaisdell

Recruit
Joined
Jun 27, 2011
Messages
2
Re: 1984 Johnson 15 HP overheating

All GREAT advise, some more info I just thought of and forgot to mention, while the motor was running, and I thought running well, The water coming out of the pee hole was extremely hot, almost burning my hand. I thought this was supposed to be cool or just warm water.

And forgive me for asking a stupid question but just because water is coming out of the pee hole, does this mean it has run throught the whole motor???
 

Monte1961

Lieutenant Junior Grade
Joined
May 8, 2011
Messages
1,180
Re: 1984 Johnson 15 HP overheating

The peepee water just tells you water impeller is working. Normal temp should be 140 to 160% Fahrenheit. post back
 

fireman57

Captain
Joined
Aug 24, 2004
Messages
3,811
Re: 1984 Johnson 15 HP overheating

Sounds like a stuck tstat. Keeping water in the head too long.
 

Monte1961

Lieutenant Junior Grade
Joined
May 8, 2011
Messages
1,180
Re: 1984 Johnson 15 HP overheating

refer back to post # 3. Good luck.
 
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