I have 1985 / 140 hp Mercruiser. My son got it for a buck. We cleaned everything, new fuel, plugs, wires, cap, rotor ect. The motor started hard and ran rough. After cleaning the carb we were able to get it running smoothly. Upon launch it runs smooth, and ran for about 4 minutes. As we were trimming the motor it exceeded 4500 rpm and just quit. Smoke can from the carb upon shut down. It would not restart. Any help?
