Operator left dock around 2pm.  The engine did not seem to be working correctly as the RPM would spike and then go back down.  Moving away from the dock to see if the spiking would stop, but the engine continued to surge.  When the throttle was put into neutral, the operator heard a "pop" that sounded like a backfire.  After turning off the engine, the operator looked in the rear of the boat and saw that it was on fire.  Operator attempted to put it out with a fire extinguisher, but failed.
Livonia                       