picked up a real clean looking 1973 9.5 Johnson. She starts and runs but will cough and die after a minute or so. adjusting the rich/lean doesn't help. took the carb apart expecting it to be dirty but it was clean. replaced the plugs, fuel pump, valve needle, coils, points and condensers. still runs the same. I missed something. at a loss. seems to smoke too much even at slower speeds(before it kills). plugs are wet with fuel.