RedactedNarrative: OPERATOR 1 WAS OPERATING VESSEL 1 WHILE DRIFTING AS OPERATOR 1 WAS ATTEMPTING TO START VESSEL 1. OPERATOR 1 WAS HAVING DIFFICULTY GETTING VESSEL 1 TO START AND OPENED THE ENGINE COMPARTMENT WHILE TRYING TO START VESSEL 1. VESSEL 1 SUFFERED AN UNKNOWN MECHANICAL FAILURE THAT CAUSED A FLASH FIRE TO OCCUR AND IMMEDIATELY GO OUT. PASSENGERS 3 AND 4 BOTH SUSTAINED INJURIES FROM THE FIRE. OPERATOR 1 AND PASSENGER 2 DID NOT SUSTAIN ANY INJURIES. VESSEL 1 DID NOT SUSTAIN ANY DAMAGE BESIDE THE FLASH FIRE TO THE ENGINE COMPARTMENT.