RedactedNarrative: After fueling at the dock, owner/operator turned on the blower for an undetermined amount of time. When the operator started the vessel, fuel vapor ignited and started a fire aboard the vessel. The owner/operator and passenger received 1st degree burns to their feet and legs. Fire was extinguished with an on board type B1 extinguisher.  2 others on board didn't file a reports and refused medical treatment.