On April 9, 1997, at 1630 mountain daylight time (MDT), an Aeronca 7CCM, N85257, was substantially damaged when it lost power while maneuvering and impacted the terrain 23 miles south of Carson, North Dakota. The pilot was seriously injured and the passenger received minor injuries. The 14 CFR Part 91 flight had departed a grass airstrip on a local flight. Visual meteorological conditions prevailed at the time of the accident and no flight plan was filed. The pilot reported that he had fueled the airplane about one and a half weeks prior to the accident with auto gas. The tanks were 3/4 full when he preflighted the airplane on the day of the accident, and he added a can of "Heat" to the fuel before engine start. He reported that the engine start and run-up were normal. After takeoff he climbed to 150 feet to 200 feet above ground level (AGL) in order look for some cows. The pilot reported that he had been flying for about 25 minutes when the engine RPM's dropped by 300 RPM's. He shoved the throttle full in but the engine did not respond. He pulled the carburetor heat on and the engine RPM's decreased by another 200 RPM's. The pilot reported turning toward a stubble field where he could make a forced landing. The wind was from the northeast and the stubble field's location was to the south. The pilot reported that he attempted to land into the wind. The pilot reported that the airplane was still losing altitude. He tried to "get the RPM's up," but was unable to regain engine RPM's The pilot reported that he thought a wind gust might have "caught me and pulled me to the ground." The airplane impacted the ground heading in a northerly direction, but was spun around during impact and came to a stop facing the south. The airplane was examined by an Airworthiness Inspector of the Federal Aviation Administration. Fuel was found in both tanks, in the gascolator, and in the fuel line to the carburetor. The fuel sample had minor dirt/particles but there was no evidence of water in the line. The carburetor was removed and opened . It was found to be dry inside with no debris. The fuel line to the carburetor had a small ice pellet formation about 1/5 the circumference of the metal neck where it flared into the carburetor B nut. The spark plugs were removed and were found to be worn and carbon fouled. The air intake filter was grimy. The engine cowl ducts were covered over with gray cloth tape. The maintenance records indicated that the aircraft had not received an annual maintenance inspection.