On December 9, 1994, at 1446 eastern standard time, a Cessna 175A, N6949E, collided with the ground during an emergency landing after a complete loss of engine power near Greenwood, South Carolina. The business flight was operated under 14 CFR Part 91, with no flight plan filed. Visual weather conditions prevailed at the time of the accident. The airplane sustained substantial damage, and the pilot received minor injuries. The flight departed Barnwell, South Carolina at 1350 hours. According to the pilot, about 39 minutes into the flight, he experienced carburetor icing conditions and a subsequent total loss of engine power. After the engine quit, the pilot selected a paved road adjacent to a golf course. As he approached the intended landing area, a vehicle pulled on to the road. The pilot reversed course and selected what he believed to have been a fairway on the golf course. As he touched down, he realized that the landing site was part of a driving range. The airplane came to rest inverted in a sand trap. An engine inspection revealed that both magneto shafts were sheared. A metallurgical examination indicated that the shafts failed in torsional overload. Both magnetos turned freely and, upon disassembly, exhibited normal operational signatures. The teeth in one magneto gear exhibited gouges and depressions and a crack through the root of one tooth. A hole was broken through the accessory case adjacent to the right magneto gear, and the inside of the accessory case was gouged in the vicinity of the hole. The external teeth on the camshaft gear, which drives the magnetos, exhibited nicks and gouges through 90 degrees of arc. The engine exhibited no conditions which would have caused the magneto shafts to break. The engine oil was strained through a filter and metal particles were discovered. The Federal Aviation Administration inspector discovered unapproved maintenance work which had been done on the aircraft, by uncertificated persons, prior to the accident. During the work, the airplane starter drive had been broken; when the engine was started it kicked back and broke the gear on the starter drive. A magnet was used to retrieve the broken gear from the rear of the engine. The accessory case was not removed to extract the remainder of the broken gear particles.