Well, hopefully the “pissing” was adequate to keep the motor from overheating. That’s just water from the lake being used to cool the motor through passageways and then being returned to the lake. The rubber impeller is driven by the drive shaft and pumps the water through the motor with those vanes on it.
Not sure if your seller went through the carburetors or not. It could be a fuel delivery issue.
If you’d like to work on it yourself, you’ll get very good advice here but I also recommend you buy the big mercury manual for motors 1965 and prior. They’re on ebay for 35-55 dollars on average. They’re thorough and will help you understand your motor and it’s issues.
Scott
