Re: '73 Merc 9.8 carb, and point question
I've got a 68 model. The carb may be different but there is only the slow idle speed adjustment . It should be the larger capped screw on the top/front of the carb. Open up the brass plug and you should find your needle. Screw it in full (just touching closed) then back it off 1/2 to 3/4 of a turn. This should get you in the ball park. Good luck.