Help please!!!!

[elevatedmind]

I have a 98 Challenger twin motor which I have not used in about 2 months. Friday night I charged up the 3 batteries cleaned up the carbs and the engines started up and sounded great like always. I went out Yesterday and it ran incredible but after riding for about 1hr the engine behind the passager reved it self all the way to 7k and it did not stop even after turning the engine off, pulling off the DESS, turning the boats power off. The boat reved up for about 5min and then there was a loud POP. Now the block has a bronze color like its fully cooked inside. what could have happened to the engine for this to happen? any input will be helpfull guys. I'll be dropping off the boat at the shop monday morning where I know the price to fix it will be alot.

 

[Nate Surveyor]

Was there no way to choke it and kill it?

I am sure that it would have been cheaper to fix!

N

 

[kustomkarl]

Sometimes the spark plugs will be quite hot and the engine will operate like a RC(radio control) engine. where the hot spark plugs act like a glow plug. because of the hot spark plugs and the fuel present the engine has a chance or running the rpm's up when out of the water with no load on the jet pump. Just choke the engine and it will stall, with too much fuel. Never let the engine just rev out of control...in it's lean condition it will over heat quickly, and could cause a seizure problem as you just encountered.

Karl

 

[mxdoc29]

i'm not sure if this will help but i raced motocross for years and i had a bike do that to me before and it ended up being basically jetting believe it or not. the premix was not getting completely burned and was building up on the carb slide which is the butterfly on these carbs. it would make it stick open....wide open until you kill it as mentioned above. i had to yank off the plug wire and shocked the heck out of my arm. So long story short make sure the gas oil ratio/injection rate is correct and or airflow into the carbs is not being slowed as this could build up a gummy sludge.

 

[seadoosnipe]

Good advice....

That's good advice, but I think the runaway engine problem on these two strokes is a bit different.

I"ve read about it in the manual, but iti was a couple years ago and do not remember exactly what it said except, not to rev the engine while out of the water.

I have been looking for that same article, but not having any luck. I have umteen manuals I've read through, so finding the right one in the right place is like needle in a hay stack............