reed valves are the achilles heel of that motor. the way you know you have reed valve issues is you will have lots of smoke, a hard start, as well as fuel dripping out the bottom of your carbs. this may not be your solution but the force motors of that age are problematic. they are cheap mercs. if your super unlucky you have the cheap Chrysler, I know a thing or two about them on the carb/reed valve end of things so PM me if you need some help.