1999 Merc 9.9 sputter/cough at low idle

[rg2]

My 9.9 ssems to cough or sputter just slightly above low idle. It will idle (in gear) then cough then it seems as though the idle speed drops slightly then picks back up - cough and so on. If I throttle up/down just slightly it will stop.

Is it possible that this is the point where the fuel supply switches from the carb bowl to the jet? If so, how can this be corrected. Would this be a symptom of a sticking needle valve in the bowl? It gets to be pretty annoying when you want to slow troll and this thing keeps coughing or sputtering similar to a slight backfire.

There are no other problems in the entire throttle range other than there.

I appreciate your opinions/comments. Thank You.

Randy G

 

[rg2]

Re: 1999 Merc 9.9 sputter/cough at low idle

Any ideas??

 

[ONERCBOATER]

Re: 1999 Merc 9.9 sputter/cough at low idle

can you richen the low speed mix a tad? or did they fix the mixtures in 1999?

 

[CharlieB]

Re: 1999 Merc 9.9 sputter/cough at low idle

Possibly a dirty idle circuit in the carb.

When was the last time it was cleaned?

 

[rg2]

Re: 1999 Merc 9.9 sputter/cough at low idle

Yes, you can adjust the low speed mixture - and I have done this and seems to improve the operation.

No, I have not cleaned the carb yet and I am thinking along those lines as well. I plan on doing so once the crappie fishing slows down. I don't want to do anything to it just yet that would keep me from using it.

I appreciate the help.

 

[ONERCBOATER]

Re: 1999 Merc 9.9 sputter/cough at low idle

my suggestion would be to adjust the low speed mixture to suit your ideal trolling speed... then when you can afford the time down... do a teardown and clean/rebuild carb.

sean