RedactedNarrative: Vessel was parked at gas dock and had a certain amount of gas put in but was not completely filled.  Gas fill area was on outside of vessel, operator advised no gas was spilled.  Even if gas would have been spilled while filling it would not go into vessel due to location of fill area.  Vessel sat at dock until they were asked to move it as someone else was pulling up for gas.  Operator got in vessel turned on blower to vent boat then turned key to start vessel and there was an explosion and fire.