RedactedNarrative: V1 backed out of the boat dock and turned to go out in the main channel of the lake.  When V1 proceeded into forward gear the boat exploded and caught fire.  Everyone on the boat jumped in the water and swam to safety at the dock. No one substained any injuries. The boat operator said he did not know if the blower on his boat was working or not and he did not test it prior to taking off.