Re: 89 force 50 revs up by itself & I cant shut it off!!
Hi guys, 1st post.......just bought a fishing boat with an 89 force 50.....starts up, idles rough & dies....if I give it throttle shell rev right up & when i pull throttle back it stays reved up (wide open) I cant even shut her down with key. Any ideas on this?? Any help would be greatly appreciated from this newbie!!!
Welcome aboard,TDawg
That is a classic example of thermal runaway. Scarey and detrimental (as you can guess)... I had a 50HP that would so that often, due to the fact that I used it mostly in an idle zone (danged mannatees anyhow!!)
My motor developed lots of carbon from all that idling, and even tho I frequently decarbed it, it would still run-away on the muffs sometimes while flushing the salt out of her.
What caused this is the carbon in the cylinders and exaust ports will glow like charcoal...This glowing carbon would act like a glow plug on a model airplane engine... The ONLY way to shut it down is to spray an increasing amount of water (you want just enough to shut it down and no more) directly into the carb -- or just let it run out of fuel.
I got in the habit of flushing it with the fuel line diconnected, so it would only idle about 5 minutes anyhow, and if it started to run-off, it wouldn't "run far".
If it is just doing it when you gun it with no load on it, that is a normal condition -- don't gun it without a load on it
, because the basic design of this old 2-stroke is to use engine compression to operate the diaphram, drawing more fuel into the carb, creating more vacuum in the process, more vaccum drawing more fuel trough the pickup, and it cascades like a diesel without a governor on it.
It may be an 89 motor, but it was designed in the 60's.
