1998 50HP johnson, need help??

[grassman]

just replaced waterpump and thermostat. started motor. fired right up. when I pulled the choke lever all the way down the engine kept revving. got up to 7,000 RPM. pulled emergency lanyard off, did not stop, pulled everything possible to shut it down, it finally shut off. I am clueless as to what is happening. I have had several outboards and this is the first time I have come across this. Ran fine when put away in october, it was winterized properly. Any ideas????

 

[dew2]

Re: 1998 50HP johnson, need help??

Ran it on muffs? Do a search for thermal runaway.

 

[grassman]

Re: 1998 50HP johnson, need help??

I was running on muffs

 

[dew2]

Re: 1998 50HP johnson, need help??

heres one read
http://forums.iboats.com/showthread.php?t=459332&highlight=runaway

 

[5150abf]

Re: 1998 50HP johnson, need help??

It is called run away and is quite scary, I have had that happen once, normally caused by carbon build up in the combustion chamber, the carbon gets hot enough to ignite the gas so you don't need a spark and it just runs up till it can't go anymore, you are lucky it didn't let go.

Make sure your cables are right on the engine and nothing holding the throttles open and try it again, maybe take the intake cover off so can clamp a hand over the carbs and kill it is it does it again.

I would certainly do a decarb on it straight away.

 

[grassman]

Re: 1998 50HP johnson, need help??

what's the best way to decarb it without starting it. I am scared to death to fire it up again. Do you think any damage occured during the run away? I did pull the plug wires off and cranked it after this episode and it seemed to crank normal.