Just to add to this before someone else chimes in and tells him to clean the carb, etc. This is what I did to it before I sold it to him:
Cleaned the gas tank with muriatic acid.
Cleaned out the carb (several times)
Cleaned out the exhaust
It runs better with no air filter.
How about points? Would that cause behavior like this?
Someone please help him before I find this Murray thrown in my front yard on fire!