RedactedNarrative: Operator of vessel arrived at boat launch at approx. 2:30 PM and launched vessel.  Operator had one occupant on board.  Vessel was operated out of marina and north for a short time before turning around and heading back south (downstream).  When passing the mouth of the marina, operator and occupant started to smell smoke.  
  
  Smell and sight of smoke got worse as they passed under Hwy 13 bridge.  When operator turned vessel to go back to boat launch, motor died.  Operator stated motor was not running well and he could only go clutch forward speed.  After waiting for a while thinking motor had just overheated, operator started motor again and began travelling back upstream to boat launch.  Operator stated vessel made it to just under the bridge when motor quit the second time.  
  
  This time, the smoke got thicker and he heard a loud "pop".  The plywood center piece above the motor blew off and into the water.  Flames were seen shooting out of engine compartment.  Operator splashed water on it until fire subsided.  Operator stated he left the vessel and swam to the pile on with a rope to tie up the vessel.  Operator and occupant then exited vessel and walked back to boat launch.  Owner of boat was contacted during incident and told operator to tie it up and leave it there until next day.
  
  The next morning other boaters saw the vessel adrift and anchored it downstream from where it was initially tied up.  Due to the obvious fire damage to the motor, Conservation Police were notified and arrived to investigate.  I was able to determine who the owner was and find out what had happened the day following the incident.  Both operator and occupant stated no injuries occurred during the explosion.
  
  From images of the motor, a picture taken by the operator, and from statements of parties involved, the fire started from an exhaust manifold overheating.  The exhaust manifold had just been replaced the week prior.  Once the exhaust manifold got extremely hot, it started surrounding materials (carpet, foam, wiring, wood) on fire and once it got through the fuel tubing the explosion occurred.  Photographs of the motor after the incident are attached.  Also attached is a photograph taken by the boat operator after the explosion showing the exhaust manifold "red hot".
  