Johnson revs high and won't shut down

[stockypower]

Hi - I have a 1983 Johnson 175 that is running at a high idle after starting and then won't shut down when I turn the key to the off position. I have to choke the engine out with the primer on the key switch and then turn it to off to kill the engine. The powerhead was rebuilt last year and one power pack was replaced. Any thoughts? Thanks !!!

 

[JB]

Re: Johnson revs high and won't shut down

The engine may be going into thermal runaway, where it runs similar to a diesel. This is quite common on a 2 stroke engine revved without a load, even if the revving is caused accidentally.

 

[stockypower]

Re: Johnson revs high and won't shut down

Can anything be done to correct that and would that keep the engine from turning off? I read similar postings where the power packs were the suspect.

 

[JB]

Re: Johnson revs high and won't shut down

If thermal runaway is your problem, SP, the base cause is in whatever is revving the engine up with no load. Could be throttle linkage or linkage to ignition system timing. Could be a loose throttle butterfly.<br /><br />Thermal runaway has nothing to do with power paks, it does not use the spark.<br /><br />You need to take your manual and tune the engine from scratch.<br /><br />Good luck.

 

[stockypower]

Re: Johnson revs high and won't shut down

It looks like I had two separate issues. The high idle issue may be corrected with an adjustment and tuning. The problem of it not shutting down was a bad ground connection on one of the power paks. I found the black & yellow wire not mating properly in in its socket. Re-worked the wire in the socket connector and the engine starts and stops fine.<br />Thanks !