Re: classic RUNAWAY
Ah, it's about time somebody asked that question about runaway. Usually they ask what that switch is for on the side of the powerhead--the one they took off and threw away because they didn't need it.
That is a vacuum cut-out switch. The switch senses a runaway condition by monitoring the vacuum inside the intake manifold. When that happens, the switch closes and shorts out one side of the magneto, killing the spark on one plug wire till the motor slows back down.
The switch has to be wired correctly and the starter safety switch has to be there too, or it won't work.
Hi Thanks for the replies. I'm the guy that posted the original overheating/runaway post on the Evinrude motor.
I got hold of a compression tester and both cylinders test out okay much to my relief. I have ran the motor briefly again o the muffs without the T-Stat and with the stat hole plugged up to check it out and it seems okay.
Ref the switch you talk about my first thought when it went haywire was to pull off the plug leads. I did that and it made no difference. Something was obviuosly creating the combustion process other than a spark.
As I said in the original post I eventually stopped it by choking the motor. I was in such a panic though after switching the ignition off and pulling the plug leads and it kept running, I didn't know what to do next. When the thermostat housing melted and popped out I was in two minds wether to run and hide or try something else! Luckily my brain kicked in and I choked the carb and it stopped. It sat there silent at last, smoking like a dead monster. What a relief!
So how to stop it happening again?
Do I only flush on muffs at tickover for a minumum period?
Or is there other options to prevent a reocurrence?
Thanks again.