Re: 1975merc.50hp/4 cylinder
By what I could understand from your description, it sounds as if it could be any one of a number of issues.
I'd suggest you start with the somewhat simple stuff like squeezing the bulb to make sure it's getting fuel.
See if it's pumping water, and not over heating.
Trying the choke to see if it helps.
Make sure you are getting enough oil in the gas.
Do a plug check to see if it's going lean.
A motor that old probably has pretty well bared wires all over it, throughout the harness, and in the controller, unless they have been changed, so an electrical problem is not out of the question.
It's a lot cheaper to go through the carbs and fuel pump, then start throwing ignition components at it, but I could see a marginal ignition component failing after 5-10 minutes to come back to life after a cool down period.
Look for spark during it's down time.
