On October 24, 2007, about 0920 eastern daylight time, an Ercoupe 415-C, N94320, was substantially damaged following a partial loss of engine power while in cruise flight, and subsequent ditching in a river near Stuart, Florida. The certificated sport pilot and a passenger were not injured. Visual meteorological conditions prevailed, and no flight plan had been filed for the flight that departed the St. Lucie County International Airport (FPR), Fort Pierce, Florida. The personal flight was conducted under 14 Code of Federal Regulations Part 91. The pilot reported that the airplane was in cruise flight at an altitude of 1,000 feet mean sea level, approximately 5 miles from Witham Field (SUA), Stuart, Florida, when the engine experienced a partial power loss. The pilot performed the emergency checklist items, which included applying carburetor heat, but did not note any change in engine performance. The pilot initially attempted to continue to SUA; however, as the airplane descended, he elected to ditch in the St. Lucie River, about 2 miles north-northwest of the airport. The pilot and passenger exited the airplane, which subsequently sank in saltwater. The airplane sustained damage to the forward portion of the fuselage, both wings, and the propeller. The airplane's most recent annual inspection was performed during March 2007. The pilot reported that he flew the airplane for 3 hours, 2 days prior to the accident and did not experience any problems. The pilot further reported that when the airplane was recovered, he observed contamination lodged in the fuel line leading to the gascolator. He did not observe any fuel contamination during his preflight inspection. The airplane was subsequently sold. During an interview, the new owner confirmed the presence of a restriction in the fuel line. He further stated that after the fuel tanks and fuel lines were flushed, the engine was started and ran without any anomalies. A weather observation taken at SUA, at 0847, reported: wind from 170 degrees at 4 knots, visibility 10 statue miles, scattered clouds at 3,500 feet, temperature 26 degrees Celsius (C), dew point 24 degrees C, altimeter 29.86 inches of mercury.