On March 7, 2000, about 1210 eastern standard time, an Aeronca 7AC, N474HH, was substantially damaged while executing a forced landing near Pawling, New York. The certificated recreational pilot received minor injuries, but his passenger was not injured. Visual meteorological condition prevailed, and no flight plan was filed for the personal flight conducted under 14 CFR Part 91. According to the pilot, 20 minutes after departing Robertson Field, Connecticut, and at a cruise altitude of 3,500 feet msl, the airplane's engine began to surge. The pilot did not see an airport to execute a forced landing to, so he began trouble shooting the problem. He switched the magnetos on and off, and observed no change. He then applied carburetor heat, but the engine ran even rougher so he selected carburetor heat off. After 5 minutes of the engine running rough, the pilot cycled the fuel selector; simultaneously he experienced a further drop in engine power. Approximately 1,500 feet, the pilot decided to perform an off-airport landing. He entered a standard traffic pattern for an open hay field that looked smooth and long enough for a safe landing. On final, the airplane struck trees short of the pilot's intended touchdown point then impacted the ground. Both occupants exited the airplane unassisted. According to a Federal Aviation Administration Inspector, the airplane was placard for auto-gas only. The inspector rotated the propeller and obtained "good compression." He also stated that the fuel smelled "rancid and very nasty." He added that the airplane was equipped with new magnetos, wires, and plugs.