Re: adjusting duel carbs? Force 120
First you do one, then you do the other. Unless you are extremely coordinated and can do both at the same time.
The best way to adjust the idle mixture screws is with the boat tied up to the dock and in gear at idle 750 rpm speed. Adjust slowly, letting the engine catch up with the adjustment before turning more.
Do both, then do both again. This fine tunes them. Don't go below 7/8 or better 1 turn out as the engine will be too lean at WOT then.
John