engine runon problem

[reclaw64]

I have a 1999 4.3l Merc vortec with a 2b carb that needs a new intake manifold. This boat has had an engine runon problem since I've owned it. Premium gas and octane boost does not help. Also I need more power. Should I switch to a 4 barrel manifold and carb? Will this help my runon problem?

 

[rbh]

Re: engine runon problem

a couple of people have been having this problem lately, idle down for a bit before turning off engine and there is a bulletin from the mfg (look up engine dieseling/run on, and dieseling was spelled different)?
rob

 

[Bt Doctur]

Re: engine runon problem

Generally speaking:
too high an idle speed
incorrect timing
engine temp too hot
lean fuel condition
spark plug heat range too hot
carbon build up on piston tops

 

[Bondo]

Re: engine runon problem

Should I switch to a 4 barrel manifold and carb? Will this help my runon problem?

Ayuh,... The 4bbl. will net you about 25hp or so...
It May, or may Not help with the run on,....

Mine's the stock 4bbl. model,+ has never had the issue...

 

[reclaw64]

Re: engine runon problem

Is the switch from 2 barrel to 4 difficult? Linkage? fuel lines? cables? tuning?