The aircraft had been repossessed. The purpose of the flight was for the pilot to demonstrate it to one or both of the other occupants. Prior to this flight, the aircraft had not been flown since 5/20/82. During takeoff, the engine lost power at about 200 ft AGL. The pilot made a right turn back toward the runway, but the plane crashed in a wooded area beside the departure end. It was in a steep right bank during impact with the trees. After the accident, water was found in the left wing tank, fuel sump at the engine fire wall, electric fuel pump and attached lines, engine driven fuel pump and carburetor. The fuel selector was found positioned to the left tank. Also, the attach cable for the right inboard seat belt was found broken. Samples of the seat belt cables were tested; one of 3 samples failed at 1570 lbs (the other 2 samples tested to 2126 & 2174 lbs). Corrosion was found on the weaker sample.