RedactedNarrative: Officer and I were on routine patrol when we happened upon a boat fire at approx  09:33 hours CST.  KSP Post 3 was notified as we approached the vessel.  Lincoln Fire Department was dispatched at 09:33 and arrived 09:43 according to their dispatch.  Vessel owner and operator had just pulled out of the ramp at Sunset Harbor on Nolin River Lake near Cub Run, KY.  
  Operator was operating a 1995 Caravelle Runabout Inboard with a 250 HP Mercury Engine. Operator had two adults and three children passengers.  Operator stated that he had the boat running just after launch when the boat unexpectedly stopped running.  He tried to start the motor again, with the motor cover open, when he noticed a flame and explosion.  All passengers exited the vessel and entered an unknown pontoon that was near.  All three children were wearing PFD's at the time of the accident and PFD's were available for each adult, but not used.   
  Six fire extinguishers were used and eventually many buckets of water were poured on the boat to prevent further damage and subdue the flames.  Lincoln Fire Department arrived approximately 09:43 and completely dissolved the flames.  The vessel appears to be a complete loss.  Subject trailered the boat and took it with him.  No injuries were reported or noticed.