Sounds like he was revving the motor when out of the water, it can get into a runaway mode and start dieseling, it can be hard to stop, sometimes hitting the choke helps.
My friend had the muffs on while running the motor, then it started revving by itself. The motor finally shut off, and he's not able to get it started again. We're thinking the gas may be lacquered due to it sitting through the winter.
