RedactedNarrative: On 12-25-17 at approximately 1439 hours, the boat caught on fire while underway in the area of the north pleasant harbor four lane boat ramp.  Operator said he was unable to extinguish the fire with his extinguisher, as the flames were originating from the top of the carbuerator, which was inaccessible to his extinguisher.  The boat burned to the water line and sank.  No one was injured in the fire.