Vessel was at dock.  Owner operator was starting engines.  Starboard engine started and owner noticed a flame across top of the battery.   He attempted to cover it with towel, but said it then blew up.  He then dove out of boat on to the dock.  The  vapors inside vessel exploded and shook houses in the surrounding neighborhood..  

The boat V1, a 1983 Chris Craft, cabin cruiser,  was docked in the canal.
Operator stated that he was attempting to start the engines of the boat. The starboard engine ( of the twin 350's)  started and he noticed a flame on the battery.   He tried to cover it with a rag and it blew up.  He then dove out of the door and on to the dock.   His neighbor called 911.   
Operator told the fire fighters that he had the blowers on prior to starting the engines.  
Operator told us that the boat had been sitting for awhile and he was in the process of fixing it up. He was supposed to be selling it on Monday for $6000.00.   It was not insured.  The boat had approx. 60 gallons of fuel aboard. The boat was a total loss.

Operator was burned on his leg.  He was treated on scene by Fire Rescue personnel and subsequently went on his own for further treatment. 
Witness, was across the canal, and witnessed the incident.  He stated he was watering his plants on the dock when he heard a faint alarm.   He turned away and was looking for the source of the alarm when the explosion happened.   He looked back at the boat and saw debris still flying.  A matter of seconds later a man came from the cabin of the boat.  Soon after that, there was smoke and then flames. 
Sea Tow of Key Largo responded and removed the vessel from the dock after all the fire was extinguished.  The boat was towed to Manatee Bay Marina for disposal;
KEY LARGO