How do i adjust mixture screws on carb

[Gyroe1970]

I just rebuilt the quadrajet on my 87 230 weekender. its has the 5.7 omc engine. i also replaced the fuel pump, plugs and wires. im ready to adjust the idle mix screw on the carb have read different things about this. I gently seated the screws and backed them out 3 1/2 turns as per the carb rebuild instructions. so, do i make my adjustments in the driveway with muffs, sitting in the water idleing or while underway? thanks guys!

 

[fc3]

They're not called idle mixture screws for nothing. Run the engine at idle with no load. Once the engine is started, adjust in quarter turn increments both left and right screws then pause to observe the effect.

Start the engine and adjust 1/4 turn rich until the engine starts to stumble or slow down. The adjust lean until the idle gets smooth. Then continue to adjust towards lean until RPMs peak. Adjust 1/2 turn to rich. Done.

 

[sdarc]

^^^ and you can use a vacuum gauge to adjust. try to get the highest vacuum reading.