RedactedNarrative: Vessel one had just completed fueling at the dock and was having problems starting.  A "large explosion "  occurred, propelling one of the injured males off the dock.  All four males were transported to the emergency room at the local hospital and were treated for first and or second degree burns to their legs and then released.  The fire was extinguished by a few dock hands and the local fire department.  The vessel was a total loss.  Investigation revealed no further information.