RedactedNarrative: Operated Vessel for a 20-25 minute pleasure ride to restaurant on lake without incident.  Docked boat and shut off motor.  Passengers exited boat, operator remained.  After approximately 10 minutes, smoke seen emitting from under cowling of engine.  Smoke became thicker, cowling then removed to discover flames seen from front of engine.  Flames immediately then extinguished using on board fire extinguisher. 