RedactedNarrative: Vessel Owner stated that he had stated the boat and was letting the engine warm up when he heard a "whoosh".  After hearing the sound, he checked the engine compartment and found a fire.  He expelled the fire extinguisher on the fire but the fire kept burning.  
  
  At this time, he and his brother abandoned the boat and tied the boat to the pier.  Due to heavy fire damage and the hull having several feet of water and foam inside, Fire Investigators were unable to gain access to inspect the engine compartment.  After speaking with the Vessel Owner, the most probably scenario would have been a catastrophic fuel leak which was able to ignite fuel fumes in the engine compartment.  The engine did remain running during the fire which would mean that fuel would have kept leaking during the motor's operation.  Fire investigators considered an electrical malfunction but due to the speed at which the fire grew in size, they classified this fire as accidental.