4.3L Merc - Engine Stalls when Hot Under Full Throttle.

[hn295]

4.3L LX Alpha 1 was professionally winterized last fall. All was fine last time out last fall. In the water for the 1st time this weekend. Started up fine, but after about 10 minutes running it started to die at full throttle. Runs fine again when throttle is backed off and engine is under about 3000RPM. Starts fine and runs fine under low-med throttle. Once engine is cooled down, everything is fine at all RPM and throttle ranges - but problem repeats itself when engine heats up. Boat was stored for winter with full fuel tank and gas stabilizer. New fuel pump last season. Anything that might have been done as part of winterizing process that may have caused this? Suggestions as to what to try first? Thanks.

 

[Haut Medoc]

Re: 4.3L Merc - Engine Stalls when Hot Under Full Throttle.

Welcome to iboats.....
Does it overheat?
Have you changed the water separating fuel filter?.....​

 

[hn295]

Re: 4.3L Merc - Engine Stalls when Hot Under Full Throttle.

Engine temperature and oil pressure are all in normal range. Fuel filter change is first on my list - but I'm thinking it's probably something more than that.

Thanks,

 

[Haut Medoc]

Re: 4.3L Merc - Engine Stalls when Hot Under Full Throttle.

Well, the filter is a good place to start.....
You hould see if that helps, if not & it occurs again, try pulling off the gas cap....
a clogged tank vent is possible.....
You can also try running it with a portable container, (6 gal. or so)& see if the problem goes away.....
If it does, that would help isolate what part of the fuel delivery is the problem, I believe your problem fuel related......
Try the cheap easy tests I posted & post back your results.....
I don't think the engine being warm or cold has anything to do with it.....
You could pull your plugs to have a look at their condition as well....​

 

[hn295]

Re: 4.3L Merc - Engine Stalls when Hot Under Full Throttle.

I agree - certainly seems fuel related. I'll be trying all the fixes recommended - but there is definately an engine temperature variable here as well. Problem exists 100% of the time when engine is hot and is non-existant when the engine is cold. I was hoping someone else may have experienced similar symptoms first time out in spring that may be winterization related - and that they could help narrow down the problem.
Thanks,

 

[Haut Medoc]

Re: 4.3L Merc - Engine Stalls when Hot Under Full Throttle.

Is the choke fully open when warm?.....​

 

[hn295]

Re: 4.3L Merc - Engine Stalls when Hot Under Full Throttle.

Yes - choke appears to be functioning properly.

 

[Coors]

Re: 4.3L Merc - Engine Stalls when Hot Under Full Throttle.

I dunno, but I have seen it work.
Old ladies never getting over 25 mph
Start revving it, and pour Coke in the carb; the water and fructose loosens carbon.
I can feel the attacks coming..

 

[180shabah]

Re: 4.3L Merc - Engine Stalls when Hot Under Full Throttle.

I can feel the attacks coming..

I think you have opened the door for the Coke -vs- Pepsi battle