On May 16, 2003, approximately 1530 mountain daylight time, a Cessna 210N, N4804P, sustained substantial damage during a forced landing following a loss of engine power near Lewistown, Montana. The commercial pilot and his two passengers were not injured. The airplane was registered to and operated by Konitz Contracting Inc., of Lewistown, Montana. Visual meteorological conditions prevailed for the personal cross-country flight which was operated under 14 CFR Part 91, and a flight plan was not filed. The airplane departed from the Ravilli County Airport (6S5), Hamilton, Montana, at 1415, and was destined for the Lewistown Municipal Airport (LWT), Lewistown, Montana. According to the Pilot/Operator Aircraft Accident Report (NTSB form 6120.1/2), the pilot reported that he entered downwind for runway 25 at LWT, and when he reduced power to obtain gear and flap operating speed, the engine immediately ran rough. The pilot reapplied power and the engine "smoothed out." Repeating the process a second time, the engine ran rough again, prompting the pilot to reapply power and raise the nose to obtain gear operating speed. The pilot then lowered the landing gear and flaps to 10 degrees. The pilot stated, "....saw I had runway 25 made, [I] turned base, reduced power, and the engine stopped. I was not used to the dead engine glide ratio and fell 300 to 350 feet short of runway 25." The pilot reported that he made a good landing on the grass, but the abrupt end of the pavement of runway 25 resulted in the airplane striking the estimated 6 inch lip, knocking the nose landing gear back and damaging the right main gear and propeller. The pilot further stated that the end of runway 25 was not maintained. He added, "The dirt cut down from the snow plow caused damage to the aircraft. Otherwise no damage would have occurred." An FAA inspector, who traveled to the accident site, reported that both propeller blades were damaged, and that the lower structure of the airplane, forward of the firewall, had sustained substantial damage as a result of the nose gear being folded rearward. The inspector also reported that the distance from the threshold ground level to the overrun pavement surface of 6 inches exceeds the recommended maximum of 3 inches and contributed to the substantial damage to the aircraft. A post-accident examination of the airplane by a certified airframe and powerplant mechanic revealed the fuel in the tanks was adequate (estimated to be one-half or better). The fuel selector was on the left tank and fuel samples at the gasculator and tank sumps had proper color and odor with no contamination or water present. The fuel injection finger screen was found clean. The engine-driven fuel pump and drive train with the engine oil level was normal. The oil filter was opened with no unusual contamination noted. The were no oil or fuel leaks noted. Throttle and mixture cables had continuity to the engine. The engine turned freely with all cylinders having adequate compression with no obvious cylinder failure. Spark plugs and exhaust stacks were sooty in color. The turbocharger turned freely. The turbo wastegate was in the open position. Both magnetos turn internally and were making spark to the spark plugs.