Background
The pilot flew the float plane to Cottonwood Lake for maintenance. During the maintenance, a quick drain was installed in one wing tank, and the other wing tank was drained. The pilot was aware of the resulting low fuel condition but did not visually inspect the tanks before the subsequent flight.
Event
The mechanic who worked on the aircraft informed the pilot of the low fuel condition. However, the pilot believed there was sufficient fuel to fly to Wasilla Lake, which is located just three miles west of Cottonwood Lake. Shortly after takeoff, the engine lost power. The pilot attempted to turn back to Cottonwood Lake to land but did not have enough altitude. According to the pilot, the aircraft stalled and crashed into trees as he was turning away from a house.
Findings
After the accident, less than one gallon of fuel was found in one tank, and the other tank had about one quart of fuel remaining. According to the aircraft owner's manual, 1.5 gallons of fuel was unusable in maneuvering flight, and one gallon was unusable in level flight.