Engine Sputtering

[MariahSX20]

I have a 1-year old Mercruiser AlphaOne 4.3L (carburated) I/O engine on my
'06 Mariah bowrider.

Everytime I shut off the engine (after being warmed up), it sputters and coughs for a good 15-20 seconds before finally shutting off. Almost immediately you could smell gasoline fumes coming off the enclosed engine compartment. I started experiencing this problem the last couple of times I've taken the boat out, after aproximately 50 total engine hours.

What could be causing this problem?

Any suggestions are greatly appreciated. Thanks, Andy

 

[Haut Medoc]

Re: Engine Sputtering

Welcome to iboats......
Isn't the boat still under warranty?...
I'd take it back to the dealer......​

 

[180shabah]

Re: Engine Sputtering

I think I responded to this on another forum,

More than likely you have developed carbon deposits on the combustion chamber. These create spots that are hot enough to ignite the fuel charge on thier own, allowing your engine run-on uncontrolled. It could even run backwards like this and suck in water through the exhaust(not good). There are merc bulletins concerning this. Solutions include, reduced idle speed, retarding base ignition timing and so on. However, the root of the problem is most likely the carbon build-up. Get rid of the deposits, and your problem will also go away. You can have the intake system professionally cleaned, or use the BG44K I recommended on the other site. It is a little slower(it will take several gallons of treated gas -vs- 10 minutes at the shop) than the professional cleaning, but much easier, and you don't have to wait until the shop has time to get to it.

Good luck