On October 12, 2002, at 2030 eastern daylight time, a Cessna 177RG, N7510V, was substantially damaged during a forced landing in South Vienna, Ohio, following a total loss of engine power. The certificated private pilot and the passenger were seriously injured. Night visual meteorological conditions prevailed. No flight plan was filed for the flight, which originated at Mad River Airport (I54), Tremont City, Ohio, destined for Madison County Airport (UYF), London, Ohio. The personal flight was conducted under 14 CFR Part 91. In a written statement, the pilot stated that the airplane was about 7 miles from the Madison County Airport, at an altitude of 2,500 feet, when the pilot began to smell something burning. The odor continued to intensify, and the engine lost total power. The pilot then applied full mixture, turned the electric fuel pump on, and cycled the fuel selector position from "both," through the "left," and "right" positions, and back to "both". He also cycled the magneto switch, and attempted to maintain 70 knots of airspeed. The pilot reported that he could see the airport, and activated the pilot-controlled lights; however, he knew he would not be able to make it to the airport. The pilot then aimed for a "dark spot" on the ground and kept the landing gear retracted, as he was unsure of the terrain beneath him. The pilot attempted to maintain an airspeed of 60 knots during the descent and did not flare during the landing, since he could not see the ground. The airplane then impacted a soybean field in a nose-down attitude and came to rest upright. Several witnesses observed the airplane flying overhead, and stated that the engine was not producing power prior to impact. One witness stated he could only hear "the swoosh of the wings" as the airplane "glided in." Another witness stated that the "motor was not on," and it appeared the pilot was "trying to make it to the airport." Examination of the engine by a Federal Aviation Administration (FAA) inspector revealed that the single mounted/dual magneto had come off its mounting studs, and was lying in the engine cowling. Upon removal of the cowling, the mounting hardware for the magneto was observed, which consisted of two magneto attachment blocks, one nut, and one 5/16" lock washer. Examination of the washer revealed no impressions of being torqued. The two studs that were used to attach the magneto to the engine accessory housing were not damaged. Examination of maintenance records revealed that the magneto was removed during disassembly of the engine for crankcase repair on July 3, 2002, approximately 60 hours prior to the accident. The engine was reinstalled on the airplane on July 19, 2002, at which time an annual inspection was performed. The weather reported at Dayton International Airport (DAY), Dayton, Ohio, at 1954, included winds from 210 degrees, at 6 knots, 5 miles visibility with haze, few clouds at 3,900 feet, broken clouds at 5,500 feet, temperature 66 degrees Fahrenheit, dew point 63 degrees Fahrenheit, and barometric pressure of 30.08 inches Hg.