On September 28, 2018, about 1325 eastern daylight time, a Piper PA-32-300, N4592X, operated by the private pilot, was substantially damaged during a forced landing to a marsh, following a total loss of engine power during cruise flight near Bartow, Florida. The private pilot and passenger sustained minor injuries. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and an instrument flight rules flight plan was filed for planned flight to Tampa Executive Airport (VDF), Tampa, Florida. The flight originated from Boca Raton Airport (BCT), Boca Raton, Florida, about 1230.The pilot reported that during cruise flight, the engine began to run rough. He notified air traffic control (ATC) and declared an emergency. Shortly thereafter, the engine cowling separated and the pilot observed that a cylinder had separated as oil began to cover the windscreen. Although ATC provided vectors to the nearest airport, the pilot could not see due to the oil, and flew via the instruments to the ground. Examination of the accident site by a Federal Aviation Administration inspector revealed that during the landing in a marsh, the right wing contacted a tree and separated. The inspector also observed that the No. 3 cylinder had separated. Further examination of the engine following recovery revealed impact marks on the engine crankcase where the No. 3 cylinder secured to it. The marks were consistent with the cylinder impacting the case multiple times. The examination also revealed that several of the other cylinder nuts were below the required 50 ft/lbs of torque. The six-seat, low-wing, fixed-tricycle-gear airplane was manufactured in 1975. It was powered by a Lycoming IO-540, 300-horsepower engine, equipped with a constant-speed, two-blade Hartzell propeller. Review of maintenance records revealed that the engine's most recent overhaul was completed on November 14, 2006. The airplane's most recent annual inspection was completed on March 16, 2018. At the time, the engine had accrued 353.58 hours since the overhaul. There was no record of any cylinder removal or replacement since the engine overhaul. The airplane had flown about 13 additional hours from the time of the most recent annual inspection, until the accident.