25 hp Johnson was run hot, What problems?

Bearcamp

Petty Officer 1st Class
Joined
May 21, 2003
Messages
341
I purchased a 1978 Johnson 25 hp. After looking it over good I noticed that the wires from the ignition box were melted to the head. Right aways I figured it was run hot. I replaced the wires and now I have great spark and compression of about 125 in each cylinder. I figured either the water pump or thermostat or both went bad. Question is, what all should I look for? Any other problems I should be aware of or check out?
 
D

DJ

Guest
Re: 25 hp Johnson was run hot, What problems?

Bearcamp,<br /><br />If you do not know he history of the water pump service, it's due.
 

alcan

Commander
Joined
Dec 14, 2001
Messages
2,505
Re: 25 hp Johnson was run hot, What problems?

Hi Bearcamp<br />I suppose it could be possible for the motor to get hot enough to melt wires (do to over-heat condition). I think I would look for some type of short or other electrical malfuntion ??? Bottom line, you just purchessed this motor. Wether you plan to keep and use it,or trade it off as a runner, you need to give it a complete servicing and inspection of all the systems. Just cause a motor over-heats doesn't always mean it is finished. Factory manuals, and I belive most after market manuals outline a tune-up/serviceing procedure. The pro's are taught to follow this systematic approch to diagnose problems and make repairs. This process is sometimes hard to sell. For example, here is a motor in front of me with a cracked gearhousing and oil spewing about. Why do I need to inspect the fuel system or do a compression test? Because there is no sence repairing the gear case if the rest of the thing is shot as well. Good luck with your 25hp, sounds like it's going to be a winner.
 

Solittle

Fleet Admiral
Joined
Apr 28, 2002
Messages
7,518
Re: 25 hp Johnson was run hot, What problems?

When purchasing any used motor I would do the following as a minimum unless I was SURE (with receipts) that all had been done recently:<br /><br />plugs<br />water pump<br />thermostats<br />gear oil<br />grease all fittings<br />pull prop & grease prop shaft<br />gas filter/water seperator<br /><br />check all bolts that mount the motor for tightness<br /><br />If I intend to keep the motor I would buy the OMC shop & parts manual.<br /><br />Lotsa other stuff you can play with but these things will keep you out of trouble.
 

Bearcamp

Petty Officer 1st Class
Joined
May 21, 2003
Messages
341
Re: 25 hp Johnson was run hot, What problems?

Yes I already did plan to go over it top to bottom as I'm planning to keep it myself. Exhaust gasket, head gasket, water pump, lower seals and thermostat are already ordered. I was just wondering if there's something I should be aware of.
 
Top