1975 johnson 20hp dies when warm

[doc7]

Hello.
I have a 1975 Johnson 20hp. When I run it for about 10 or 15 mins it shuts off and has no spark on both cilinders. After sitting for about 20-40 mins or an hour it will fire right back up and run fine for a while. I can feel the side of the engine when it dies and it is not too hot - i can keep my hand on it for a long time. i have checked breaker points and adjusted them but it doesn't bring any effect. driver coil looks great. Any info on what might be wrong would be appreciated.

 

[ultra353]

Re: 1975 johnson 20hp dies when warm

Sounds like the driver coil is breaking down when it gets hot which supplys spark to both cyl. It cools down then you get your spark back. Best to test the driver coil with a meter( you`ll have to get specs). check it out cold, then run it up to temp in a barrel to get it to quit and check the readings again.

 

[doc7]

Re: 1975 johnson 20hp dies when warm

thank you. i have the specs and i'll check it on Sat.

 

[doc7]

Re: 1975 johnson 20hp dies when warm

can this trouble be caused by condenser mulfunction?

 

[ultra353]

Re: 1975 johnson 20hp dies when warm

I think it would be unlikely. How`d the driver coil test out?

 

[doc7]

Re: 1975 johnson 20hp dies when warm

i can do it only on Sat. will report asap.

 

[doc7]

Re: 1975 johnson 20hp dies when warm

Reporting: problem was in cracked crankshaft key. i replaced it and everything became just fine. thank You for support.

 

[johnnyc1960]

Re: 1975 johnson 20hp dies when warm

Reporting: problem was in cracked crankshaft key. i replaced it and everything became just fine. thank You for support.

Doc, curious how did u figure it out ? JC

 

[doc7]

Re: 1975 johnson 20hp dies when warm

very simple. a broken piece of the key appeared in my hand just after flywheel removal.

 

[johnnyc1960]

Re: 1975 johnson 20hp dies when warm

Awesome....

very simple. a broken piece of the key appeared in my hand just after flywheel removal.

 

[EricJRW]

Re: 1975 johnson 20hp dies when warm

Wow, good sleuthing. I'm curious too, what prompted you to pull the flywheel?