RedactedNarrative: After refueling both the main engine fuel tank and an outboard auxillary tank at Hope Marine Services, vessel  ID  7817 AV departed the gas dock without incident.  Shortly thereafter the main engine quit.  The owner/operator of the vessel lifted the engine hatch to investigate the cause of the engine failure and in doing so the outboard gas tank in his words got "moved or stoodup" causing the outboards gas tank's cap to come off. The cap on the tank not being tightened or careless installed. The resulting fuel spillage ran into the engine compartment and was ignited by the hot main engine.  All three occupents of the vessel jumped overboard  (two with burns over 36% of their bodies). The owner/operator suffering burns to his legs reboarded the vessel and extinguished the fire.  One of the passengers swam to shore while the other clung to the vessel while a good Samaritan towed the damaged vessel back to the marina.  The two injured passangers were flown to Kootenai Hospital and subsequently Seattle burn center while the owner/operator continues to be treated by his local physician.