On September 14, 1996 at approximately 1300 central daylight (cdt) time, a Cessna 150, N1381Q was substantially damaged during an off airport landing in Wonder Lake, Illinois. The airplane had just departed from the from the Galt Airport, and came to rest in a corn field. The pilot was uninjured in the accident, and reported that the engine had sustained a partial loss of power before the accident. The 14 CFR Part 91 flight was operating under visual meteorological conditions, and no flight plan had been filed. The pilot reported on NTSB form 6120.1/2 that during climb out after takeoff that the engine lost RPM and power. The pilot reported that after the loss of power he began the emergency procedures checklist. The engine continued running at partial power, and the pilot decided to execute an emergency landing in a corn field, approximately three quarters of a mile from the airport. The investigator in charge obtained one muffler from the accident aircraft. At the portion where one exhaust pipe enters the muffler a weld repair had been performed. Large amounts of weld which appeared to have insufficient penetration, were around the intersection of the pipe and the muffler. Another pipe on the muffler was cracked, and brown residue was present around the crack. The internal baffling inside the muffler was broken loose, and pieces of the baffling were missing. The exhaust pipe which had been welded was broken loose from the internal baffling. The aircraft's manufacturer does not recommend welding any exhaust system components, and the aircraft's logbook had an entry on October 20, 1995 which read "welded crack in muffler." The airplane's nose gear was torn off in the accident. The leading edges of the wings, left wing spar, propeller, lower cowling and propeller were all bent.