What happened
The pilot departed Jamestown, North and Dakota, at 1800 with full fuel tanks. After climbing to 9,500 feet, the pilot noted the aircraft began acting irregularly around 7,000 feet. Consequently, the pilot decided to land in Enderlin, North Dakota, at 1930.
While on the ground, the pilot determined the engine issue was caused by not leaning the engine at higher altitudes. The pilot then departed for New Richmond, Wisconsin, with a planned flight duration of 3 hours and 15 minutes and an estimated 4 hours of fuel remaining on board. During the en route phase, the pilot decided to divert to Osceola, Wisconsin, due to the late hour. Following this, the pilot became apprehensive about the fuel supply and decided to land in Forest Lake, Minnesota.
During the descent into Forest Lake, the engine abruptly quit. The pilot attempted an engine restart but was unsuccessful. To avoid a populated area between the aircraft's position and the airport, the pilot chose to land on a lake to prevent ground injuries. The pilot exited the aircraft after it contacted the water and swam to shore, where he flagged down a responding police officer.
Findings
The pilot reported that the accident was caused by fuel exhaustion. On official documentation, the pilot noted that the event could have been prevented by proper fueling or by not descending until over the airport.