15 hp force revs high

[wood9781]

I have a 1989 force 15 horsepower motor. when I started with the choke all the way on it runs okay but will eventually die. When I put the choke off it revs so high it sounds like it's going to blow up. the butterfly inside the car was not stuck open it works. I play with the idle screw it made no difference. Also need to know what the idle screw supposed to be set up how many turns out. Any help would be grateful thank you

 

[wickware]

IMO, it’s like the carb is possibly sucking air or the carb’s linkage is out of sink or mounted incorrect. If you disconnect the linkage, can you control the throttle plate manually and get better or different performance? Some Pics of linkage and throttle in the same pics in different modes (choked, wide open, etc) might help others with your motor or knowledge, spot the problem.

What is the history on the motor, when did it run correct and etc.?

As a general rule 1.25 -1.5, I feel a starting point adjusting most carbs (w/o the specs).