On July 4, 2011, about 1300 eastern daylight time, a Cessna 150L, N150ET, operated by a private individual, was substantially damaged during a forced landing to a cranberry bog, following a partial loss of engine power during takeoff from Plymouth Municipal Airport (PYM), Plymouth, Massachusetts. The certificated commercial pilot was not injured. The personal flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the planned local flight. The pilot reported that during initial climb, the engine began to run rough and experienced a partial loss of power. The pilot elected to land straight ahead into a cranberry bog. During the landing, the landing gear, propeller, and engine firewall sustained substantial damage. The pilot further stated that the loss of engine power was due to a stuck cylinder valve. Examination of the engine by a Federal Aviation Administration (FAA) inspector revealed that the No. 2 cylinder intake and exhaust valve springs exhibited corrosion and carbon deposits. The other cylinder valve springs also exhibited corrosion, consistent with lack of operation; however, they did not exhibit the carbon build-up similar to the No. 2 cylinder valve springs. The inspector also checked the fuel system, cylinder compression, sparkplugs, the carburetor, and the exhaust system, and no other defects were noted. According to maintenance records, the airplane had been operated for 17 hours since its most recent annual inspection, which was performed on August 14, 2010. The engine had been operated for 256 hours since its most recent overhaul, which was completed more than 10 years prior to the accident. Review of FAA records revealed that the same airplane was involved in a forced landing to a cranberry bog in 2003, due to a stuck cylinder valve.