Possesed Mercury

[Evinrude6]

Have a 1985 Merc 25XD- working on it yesterday, It decided to -while running, have a mind of its own and go to WOT with the butterfly valve closed, so I pulled the spark plug caps off, far enough away so it wouldent jump across (the kill switch decided not to work at a bad time) and it STILL ran at WOT. I then pulled the gas line and it eventually died. WHAT HAPPENED? WHAT DO I DO?

 

[Carbkid]

Re: Possesed Mercury

There's no way that motor ran at WOT if the butterfly was closed unless you had a major air leak from the carb back. And, your saying it also ran with the plug caps off! No way.

 

[Windykid]

Re: Possesed Mercury

I have seen motors run away but without spark or air??

 

[Chris Cole]

Re: Possesed Mercury

You've already solved the problem. It is possessed! If I was you I would consult one of those high profile psychologists, witch doctor, or priest to help you.

 

[Windykid]

Re: Possesed Mercury

Seriously, you must have a huge vacuum leak. Did anyone R/R the carb lately?

 

[CharlieB]

Re: Possesed Mercury

First, remove the carb and carefully inspect the butterfly and shaft to see if the butterfly is loose on the shaft allowing it to bind and stick the throttle open. Repair or replace the carb.

Second, DECARBONIZE the engine.

I have no doubt that the throttle stuck, the kill switch and pulling plug wires will NOT kill a dieseling engine. Carbon deposits will become glow plugs and continue running long after the ignition system is off or otherwise disabled.

Lastly, when was the last time the impeller was changed, low water flow and elevated engine temp could have contributed to the dieseling.

 

[zzzzz]

Re: Possesed Mercury

that's called a "runaway"...the plugs are already hot enough to ignite the fuel that keeps getting pumped in by the mechanical fuel pump thus a runaway...needs to be choked out to kill it...put your hand tightly across throat of carb if single carb...also disconnect fuel source

 

[Evinrude6]

Re: Possesed Mercury

Thanks-How do I go about doing somthing such as that-I'm Only 15 and I know quite a lot about two strokes. If you could tell me how to do this, I will be very thankful. My Mercspertice is not as good as some of you guys.

 

[Windykid]

Re: Possesed Mercury

Start by pulling the spark plugs and having a look at them. Check to see if your carb is loose mounted. Look for vacuum leaks.

 

[badams270]

Re: Possesed Mercury

I had that happen one time on a 2 stroke four wheeler. I pulled the fuel line, and plug cap, still ranaway. It finally ran out of gas but in the end it destroyed the crank bearings due to lack of lubrication. Choking it will work, if you think about it quick enough. I was just getting away from it because it sounded like it was going to completely blow apart.