RedactedNarrative: Operator was in the process of transiting from Vineyard haven to Oak Bluffs when the engine hiccuped and lost power smoke was coming from the vent and when he opened the engine hatch to investigate there were flames.  6 of his passengers got into an inflatable raft while he and one other stayed onbard to empty water into the crack at the hatch.  When they realized it was a lost cause they left the vessel as well.  They were aided by a passerby. Fire department and tow usa arrived.  Fire was put out.  Origin of fire is undetermined.