RedactedNarrative: Operator stated after launching the boat, the idle was running fast, had a loud explosion.  Smoke and flames ignited from the engine.  He advised his passenger to jump off into the water.  They swam to another boat and were taken to the pier.  The boat burned to the water line.  Operator stated it was the first use since extensive motor repairs.  Total damage loss is $9000.  No injuries reported.