On August 14, 2017, about 1620 eastern daylight time, an experimental amateur-built Murphey Renegade, N210SQ, was substantially damaged during a forced landing near Guilford, Connecticut. The airline transport pilot received minor injuries. The airplane was registered to and operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed for the flight that departed Tweed-New Haven Airport (HVN), New Haven, Connecticut, about 1550.According to the pilot, the accident flight was the first flight after the carburetors were inspected, repaired, and reinstalled on the engine. During the preflight inspection, he checked for water in the fuel, which was automotive fuel with 5% ethanol, and noted none. Review of air traffic control communication transcripts revealed that about 30 minutes after departing HVN the pilot declared an emergency to the HVN tower controller and stated that his engine had lost power. He advised the tower controller that he was about 10 miles east of the airport and was going to perform a forced landing to the local fairgrounds. While on approach, the airplane struck powerlines and came to rest in a field. According to the Federal Aviation Administration (FAA) inspector who responded to the accident site, the forward section of the fuselage was substantially damaged. The propeller was not damaged and there was fuel present in the fuel tanks. An examination of the engine revealed that crankshaft continuity was confirmed by rotating the propeller by hand, and thumb compression was established on all cylinders. The spark plugs and ignition system were examined, and no anomalies were noted. The fuel pump was examined, and no anomalies were noted. The carburetors were partially disassembled, the diaphragms were intact, the main jet and idle jets were not blocked, and no corrosion was noted on those parts. The left idle mixture screw had a small amount of corrosion, otherwise, there were no other anomalies with the carburetors. According to the pilot, he had the carburetors inspected and repaired twice as a result of a "rough running engine." Once in February 2017 and then again in July 2017. Both times, the pilot reinstalled the carburetors and noted that the engine ran "normal." The pilot stated that there was evidence of water contamination both times, and once, one of the fuel jets in the carburetors was a blue/green color "because of corrosion." According to the maintenance work orders, a maintenance shop performed the manufacturer's 200-hour carburetor service requirement and the 5-year rubber replacement requirements in February 2017. Then, in July 2017, maintenance personnel indicated that the carburetor was inspected and "found idle circuit was corroded. Cleaned, performed ground run-up – tested good." In a letter to the maintenance facility that performed the carburetor maintenance, the pilot noted on-going issues with the engine. The following is what he stated in his letter sent in July 2017: 318 hours – rough running [engine] replaced idle jets 331 hours – new spark plugs 340 hours – engine would not start, replaced both ignition modules 342 hours – rough running [engine], cleaned idle jets 373 hours – loss of power after takeoff, sent carb[ureters] to maintenance shop for rebuild 395 hours – rough running [engine], bought new idle jets 395 hours – weighed floats, replaced spark plugs, check main pistons for free movement, checked air cleaners. "Rough running continues, spark plugs badly sooted." According to the pilot, on the day of the accident the airplane had accumulated 410 hours of total time. According to Rotax Service Instruction "Selection of Suitable Operating Fluids for Rotax Engine 912 and 914 series," automotive fuel with up to 10% of ethanol was permitted to be used for operation.