ok what is this

[brogden31]

my boat runs well and idles about 800rpm after it gets to operating temp when i go to cut it off it will stumble for 10 to 20 sec before cutting off i know carb is clean and firing on all cyl its a 99 3.0 merc i also thought it could be grade of gas so i put in fuel treatment and it didnt have the problem yesterday but it started doing it again today

 

[Don S]

Re: ok what is this

idles about 800rpm

Get it tuned up properly, timing etc, get the carb idle mixture adjusted properly, and get that darned idle rpm down to 650 to 700 rpm and allow the engine to idle for a minute or two before shutting off after a hard run, and it won't diesel on you.

 

[Bondo]

Re: ok what is this

Ayuh,....

Dieseling causes Reversion,....

Get it Fixed before you use it....
Otherwise,.... You'll be replacing the motor, rather than just Tuning it up....

 

[PeteHarris]

Re: ok what is this

As posted earlier, bottom line it needs a tune up.

You MAY be able to get away with running premum grade gas ... but that's just a really expensive bandaid.