Seems to be running "rich" after carb rebuild & having some "run after off" issues...

[rhillman75]

Seems to be running "rich" after carb rebuild & having some "run after off" issues...

It's a 1996 Mercruiser 4.3LX Vortec Thunderbolt ignition w/ MerCarb 2 barrel. I set it to factory (1-1/4 turns out from light seat on the idle mixture) & (2 turns in just after it touches the cam on the idle screw). I have noticed alot of carbon inside the carb in the 3 trips out. I have also noticed a brief run on after you turn it off whether it is driven at 3/4 throttle or 1/2 throttle. If I turn the idle screw down 1/4 it idles at 600 rpm at the first notch (detent) of my forward throttle. Is that to low or is or does idle mixture need to go in 1/4 turn to make it 1 turn out on idle mixture. Didn't really notice it until I used "marina" gas, or did I just find my answer?

 

[alldodge]

Re: Seems to be running "rich" after carb rebuild & having some "run after off" issue

Re: Seems to be running "rich" after carb rebuild & having some "run after off" issue

Adjustment turns for na initial setup is just that, they are for initial setup. Adjusting the idle mixture and idle speed is further adjusted to obtain best overall idle after that. You will not cause harm to the engine if it is running a bit rich or lean at idle. The old method is to connect a vacuum gauge to the engine and obtain the max vacuum at idle and smoothes idle. Turn those screws anyway you wish to get it to idle and in little lean if necessary.

 

[NHGuy]

Re: Seems to be running "rich" after carb rebuild & having some "run after off" issue

Re: Seems to be running "rich" after carb rebuild & having some "run after off" issue

Yup, those are initial settings. Once it runs, turn them in til it stumbles and out til it stumbles then go in between. Also get your idle down low, or it may diesel on shutdown.