300/440/550 Dieseling/Runnaway 440

[gtgoat]

I started my 440 this weekend after letting it sit all winter. It idled well for a few seconds and then the RPM went way up, like it was wide open throttle. I hit the killswitch, nothing, I pulled both spark plug caps, nothing, I unplug the fuel lines, finally about 5-10 seconds later it shut off.
I understand that it was dieseling and that's why the killswitch and spark plug caps didn't work. I want to know why it was deiseling??
I did fog the motor when I put it away before winter. Do you think the penetrating oil in the crank started to cook and vaporized? The throttle was closed so it wasn't getting any more air than at idle.
Any idea how to stop it if it happens again?
Thanks

 

[FlightPlanDan]

Choke or primer to stop it.
Have you only tried it once? A lean condition can happen at start-up even after short periods of sitting.
Choke or prime, get those fuel lines filled and try again. If it runs away, continue to choke or prime to get the rpm's down or kill it if need be.
If it continues, check for an air leak.

 

[gtgoat]

This happened twice. It happened on the first start up and then happened again but it really ran away the 2nd time. I think I unintentionally hit the throttle the 1st time and it died. I was a little panicked when it happened so I don't remember exactly what I did. I'll try priming it if it happens again. I guess I'll have to take off the dash board cover so I can get to the primer before trying it this summer.
I was able to start it a 3rd time and rand it for about 5 minutes without anything happening again.
Thanks for the reply.

 

[vrizi]

If you get a runaway again, holding the throttle wide open will be the fastest way to shut it down. If this continues, you have got an air leak causing a lean condition most likely crank seals.

 

[jeepNski]

im assuming it was out of the water. when ther is no load on it they will deisel pretty easy. but in the water with load on the impeller it problably wont hapen. my buddys 650 has done this before running it on the trailer. never had a problem in the water.

 

[XJCrawler]

im assuming it was out of the water. when ther is no load on it they will deisel pretty easy. but in the water with load on the impeller it problably wont hapen. my buddys 650 has done this before running it on the trailer. never had a problem in the water.

Tell your buddy he needs to do a leak test or he will have more problems down the road

 

[gtgoat]

Thanks for the advice. I took it out this weekend and didn't have a problem.

 

[screaming440]

i used to have this problem with one of my 440s. i had milled the head on it and was getting about 230 psi compression. if you ran it out of the water the only way to shut it down was to put your hand over the carb. one time it ranway from me on the water and hit the shore. after that i changed the head and am running it with about 180 psi now.

anyway check the compression even if the motor looks stock the head could have been milled. if it is higher than stock (120 psi) try running higher octain fuel.

 

[gtgoat]

I did a compression test and got 150 PSI on both cylinders. That was using a $30 compression tester from Sears. Do you think the tool is accurate? Do you think that it is stock compression? - Thanks

 

[screaming440]

that is a little high for stock it should be around 120.