RedactedNarrative: Subjects had purchased this vessel about 1.5 months prior to the accident.  They had not done any mechanical work on it since then and this was the first time out with the vessel.  They launched at about 11:00 AM and went from the boat launch to the fuel dock.  They put 19 gallons of fuel in the vessel.  
  
  Subject1 stated she turned on the blower as Subject2 went to pay.  Subject1 estimated the blower was on 8 to 10 minutes before starting the engine.  Subject1 pulled away from the fuel dock and turned toward the river.  Subject1 said the engine was sputtering a little, so she gave it a little choke.  
  
  From talking to her, she apparently lifted up on the fast idle by the throttle.  Subject1 said the sputtering stopped, the engine went quiet, and they heard a "poof".  The poof was like a backfire, but not loud like the gunshot noise you normally hear.  When Subject1 and Subject2 looked back, the engine housing was lifted up and turned sideways.  
  
  At first smoke, and then fire came from the engine compartment.  Subject2 retrieved the fire extinguisher and used it on the flames.  They thought the fire was out, but when the engine cover was lifted, the entire compartment became engulfed in flames.  Subject1 and Subject2 jumped out of the boat and swam to the shoreline.  Alton Marina staff called the Alton Fire Department, who responded shortly after.  The SW winds blew the engulfed boat onto the shoreline by the parking area for the boat launch.  Alton Fire Department was able to extinguish the fire, but as a result the boat sank.  A wrecker company was called to hoist the boat out of the water and place it on the trailer.  According to Subject1 and Subject2, they sustained no injuries.
  
  I found out about the fire approximately 2 days later after reading an article in the local paper.  The boat was seized pending investigation into what started the fire.
  
  After examining the components on the engine, it appears that a fitting on a metal fuel line, going from the fuel pump to the carburetor, had been over tightened to the point of being deformed.  The nut on the fitting had been rounded off and so much torque had been applied to the fitting, that the metal line twisted.  It is very plausible that this fitting would leak gas.  If gas was leaking from the fitting, and the engine backfired as Subject1 and Subject2 claimed, this would lead to an explosion and the engine compartment catching on fire.
  
  See attached report for moredetailed information.