Engine ran without it hooked to spark plugs?!

[TarHeel Challenger]

Check this out,


So I enjoyed a great day at the lake today, boat ran great (even though I forgot to put in the drain plug) bilge worked great, spend several hours out. I get the boat out of the water, not a drop in it, which was awesome, and I started to the engines out of the water, to blow the little the was left in there. Turn on, one to two seconds turn off, i do the same with the right side engine, and I turn it on, one, two, pull the plug, ITS STILL RUNNING, I turn the back of the boat, and pull the spark plugs, still running, I pull the wiring harness that meets the the battery with the spark plugs and stuff, still running, not at a high speed, but a little higher than a idle, and it just slowly dies out, doesn't pop, like its blowing but more like running out of fuel. Not much smoke, a little, and didn't smell at all. I tried to start it, fires right up! Turned right off.


I don't get it???!!!! WHAT HAPPENED ??? a gas build up in the carbs, engine was just running so it would be able to burn it off. thats the only thing i can think of. Going out again tomorrow, going to look at it in the morning. Let me know if you got any ideas because I am freaked out.

 

[WAJetboating]

Dieseling...

Common in 2-stroke gas engines. You probably have some carbon buildup in your cylinders. It gets red-hot during normal engine operation, and when you turn off the key it's still hot enough to ignite the fuel. Eventually you run out of fuel or things cool off enough to stop.

I'd decarbon that engine. Use an extra-strong mixture of Seafoam in an external tank. It will smoke like crazy as the carbon is burned off.

 

[TarHeel Challenger]

Thanks for the post. So I should be good to go tomorrow. I can sleep a little better knowing that. What and where is sea-foam?

 

[Dr Honda]

When that happens... pull the choke. It will cool it off enough to kill it. It shouldn't happen in the water.

 

[voodoo]

The other possibility is an air leak in the lower case, this will show up as an oil leak, read the plug color and be sure you oil tank is drinking - the symptom of high heating can be caused by leanout of gas or oil. Some 2cycle oils mix OK, others form a gel like jelly on the outside of the jar and will not pass into the nozzles.

 

[WAJetboating]

Thanks for the post. So I should be good to go tomorrow. I can sleep a little better knowing that. What and where is sea-foam?

It's a fuel additive available at NAPA and most auto parts stores. Instructions are on the can. Normally you use 0.5-1.0 ounces per gallon of fuel, but when decarboning I've used 2-3 ounces per gallon. You can also add it straight into the cylinders through the spark plug hole but I prefer to just run the engine.

 

[TarHeel Challenger]

I went out today, and no problems at all. Crazy stuff. I have no oil leaks (voodoo) and the oil can is getting plenty, We do a lot of pulling, wakeboarding, tubing, two tubes, all that good stuff. I have been using AMSOIL interceptor for my oil, cheaper than the Seadoo's stuff, and I have heard good things about it.

My boat is running on the rich side, and I am too much of a pu**y to adjust the oil pump because I am afaird I may blow the engine by leaning it out. I have to throttle up slowly, or else it will cheap and then snap out of it.

Thanks for the help, on my crazy event, owned a lot of two stoke bikes and doos, and haven't had a one do that. Crazy

and Dr. Honda thank for the choke thing, I didn't even think about that. I will have to remember that...

 

[Tyler-Snell212]

I have the same problem

My millenium edition bombardier did the same thing except now it won't turn back on. I can even hook up my new battery. As soon as I go to connect the positive, it attempts to turn over with no key or nothing. I was also not getting any electrical readouts. No beep when I plugged up key. Anybody have any clues as to what my be causing this? It did the same thing as the other guys (slowly idled to dead) and now I can't even get a new battery on