MerCruiser Quadra jet 5.7 black/brownish smoke

[Goochsplat]

I rebuilt the Quadrajet last year and ran fine. I started it up in the spring and ran fine. I launched the boat and drove it to its slip only in gear never fast and it was fine. The next day I start it and it runs real rough and wants to stall so I throttle it up but it still runs rough and black/brownish smoke is comming out.

Does anybody think it's the accelerator pump or maybe it's ignition my guess is the carb

 

[Bondo]

Ayuh,..... Welcome Aboard,.... Sounds like the carb still ain't right,.....

Black smoke is unburned fuel, it's too rich,....

 

[NHGuy]

Check the easy, obvious stuff. Is your distributor loose? Any wires off? Choke sticking closed? Rotten old gas?
Did you start with the idle mix screws about 1.75 turns out and then fine adjust them?