On September 14, 2000, about 1230 Eastern Daylight Time, a Cessna 150L, N10825, was substantially damaged during a forced landing near Salem, Ohio. The certificated private pilot was not injured. Visual meteorological conditions prevailed for the local personal flight. No flight plan had been filed for the flight conducted under 14 CFR Part 91. The pilot reported that prior to departure, he conducted a pre-flight examination of the airplane. During the examination, he drained fuel from both fuel tanks and the main sump, and found no evidence of contamination. In addition, he performed an engine run up, which included checking the magnetos and carburetor heat. A drop in engine RPM was observed when the carburetor heat was pulled on. The departure was conducted on Runway 28. After becoming airborne and passing through an altitude of about 200 to 300 feet above the ground, the engine began to run rough, but although the engine was running rough, it never totally lost power. As the airplane descended, the pilot turned on the carburetor heat. There was no change in engine condition and he turned it off. The pilot said he felt that the engine might quit, and tried to find a suitable area to land. The pilot set up for a forced landing on a road, and flew the airplane under telephone lines. The right wing struck a power line pole, about 2 feet from the tip of the wing. The airplane came to rest in a field adjacent to the road, about 1 mile from the departure end of runway 28. The pilot reported the engine was still operating at low power, when it struck the pole. An inspector from the Federal Aviation Administration (FAA) reported that the wing spar on the right wing was broken, and the fuselage and propeller were bent. Fuel was drained from both wings, the main sump, and the carburetor. No evidence of fuel contamination was found. There was no blockage of air to the engine, and the carburetor heat control worked properly. The spark plugs and ignition harness were in good condition, and spark was obtained from both magnetos. Additionally, the FAA inspector reported that he interviewed people who watched the pilot perform an engine run-up, and then depart. During the engine run-up, they heard a reduction in power, which they equated with the carburetor heat being turned on. The pilot reported that he had owned the airplane for 20 years, and had always kept it hangared. He always filled the fuel tanks prior to placing the airplane in the hangar. The closest weather reporting station was Youngstown, Ohio, which was about 21 nautical miles away on a bearing of 030 degrees magnetic. It reported a temperature of 21 C at 1151, and 22 C at 1251. The dew point was reported as 16 C at 1151, and 1251. According to a carburetor icing probability chart from the FAA, the relative humidity was about 55 percent, and serious icing could develop at glide power.