On May 25, 1996, at 1245 central daylight time, a Piper PA-32, N40933, operated by Sparta Aero Services, sustained substantial damage during a forced landing due to a partial loss of engine power after takeoff near Osage Beach, Missouri. The private pilot and three passengers were not injured. The 14 CFR 91 flight departed Grand Glaize Memorial Airport, Osage Beach, Missouri, on a local flight. Visual meteorological conditions prevailed and no flight plan was filed. The pilot reported that he had departed Sparta, Illinois, and flew to Osage Beach, Missouri. The distance was about 140 nautical miles and took approximately 1.5 hours. The pilot reported that he departed Osage Beach about 15 minutes later. He reported that within minutes of departure the engine started to lose power but did not quit completely. He reported that the engine was barely above idle. Passengers flying with the pilot also reported that the engine did not sputter but continued to run smoothly at partial power. The pilot reported that he was unable to restore power to the engine, so he did a forced landing at a nearby golf course. Due to golfers on the fairways, the pilot was unable to land on the golf course's fairway. The aircraft landed in rough terrain and went through a ravine which produced substantial damage to the aircraft. The pilot and passengers deplaned without injuries. The examination of the aircraft revealed that fuel was available in all four fuel tanks prior to impact damage. The fuel lines to the engine driven fuel pump were inspected and were intact with no leakage. The electric boost pump was operated and it indicated normal fuel pressure. The engine driven fuel pump was bench tested and it operated normally. The engine was run and it operated within specifications.