What happened
A certificated private pilot and the sole passenger departed from a remote lake in a float equipped airplane. Approximately three minutes into the flight, the engine began running roughly before eventually quitting. In an attempt to reach the water, the pilot turned the aircraft back toward the lake; however, the aircraft was unable to glide to the water's surface. The pilot subsequently performed an emergency landing on the shoreline. There were no injuries reported following the event.
The investigation
An inspection of the engine conducted after the accident revealed that there was no compression in the number 4 cylinder. Investigators found that the top piston compression ring was frozen within its slot. Additionally, the upper and outer edges of the top of the piston showed evidence of erosion and scoring. Small particles consisting of piston material were found attached to the spark plugs. Furthermore, the investigation determined that one magneto had been timed 4 degrees before the recommended setting of 25 degrees.