1985 Mercruiser 170, 2 barrel MerCarb:<br />runs great WOT... runs great when I first start it, choke. Warms up OK and then... idle varies from stalling to 2000 rpm, no real control... I had to backout the idle mixture screw 3 1/2 turns to keep it from stalling.<br /><br />I just put a new float...