1988 25hp Johnson cooling problems

[Breland Clement]

I replaced the water pump with a new kit yesterday. Ran it on a hose for 20 minutes and it ran fine. Lots of water out of the tell tale, exhaust holes and prop. Launched the boat and started out at half throttle, again lots of water from the tt and exhaust. n about a mile and tt quit showing water, exhaust showed some bun no where near what it was. Shut down engine and checked tt. Pulled nipple and there was lots of scale plugging it. Ran with out nipple in hopes of cleaning out. All looked good but after a mile tt stoped showing water again and steam came out of exhaust. Suspect thermostat. Where is it located and how do you change it.

 

[goldstem]

Re: 1988 25hp Johnson cooling problems

the thermostat is on the top of the cylinder head. I believe on that motor you remove the whole head cover (not the head itself) to replace the thermostat and pressure valve. you might also have a piece of the old impeller up there.

 

[Breland Clement]

Re: 1988 25hp Johnson cooling problems

Thanks! I replaced the water pump and also replaced the thermostat. There was a lot of grit build up and a blockage in the head water jacket. I also was able to back flush the block. It must have helped as I ran it for a hour on the hose with no apparent problems, My new problem is that when I turn the key off the engine does not stop. Any ideas?

 

[tashasdaddy]

Re: 1988 25hp Johnson cooling problems

follow the black wire with yellow tracer. that is the kill wire.

 

[Breland Clement]

Re: 1988 25hp Johnson cooling problems

Thanks! I found the wire but I don't have any idea what to do with it. I ordered a manual but will be a few weeks before it is in. The black wire with the yellow stripe leads in to what I thing is the power pack. Any ideas on what to check would be appreciated. BWT the engine starts and runs great with the key switch.

 

[Tinman57]

Re: 1988 25hp Johnson cooling problems

I had the same motor for 16 years, and it always ran great. The kill switch died about every 7 or 8 years however. It is a simple replacement.

 

[Xcusme]

Re: 1988 25hp Johnson cooling problems

Breland....when the Black wire with Yellow stripe goes to ground (the power head) it kills the spark to the cylinders.

 

[markarz]

Re: 1988 25hp Johnson cooling problems

hi guys, how do you disconnect shift linkage on this model, to remove lower unit?