RedactedNarrative: On 8/16/2014 @ approximately 11:40 am, VI put the boat in the water.  They attempted to start the motor the 1st time & realized they were in mud so they went a bit further out into the water.  Started the vessel a 2nd time and then was able to  back up, yet when they went to go forward the vessel died a third time.  On starting it a 4th time, the back hatch flew up 2 feet & the occupants noticed flames in the compartment.  The flames were so large that they realized the fire extinguisher was not big enough to put out the flames.  All 5 occupants jumped into the water away from the burning boat & swam to a nearby boat.  The owner  believes a possibility is that the float stuck on carburettor & put fuel in the compartment. 3 of the 5 occupants were not wearing life jackets when they jumped.