On February 27, 2002, approximately 1530 Pacific standard time, an experimental Gunderson Floatmaster, N2425D, registered to and operated by the pilot as a 14 CFR Part 91 personal flight, nosed over in a field during an off airport emergency landing near Elma, Washington. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft was substantially damaged and the commercial pilot, the sole occupant, was not injured. The flight departed from Rochester, Washington, about 30 minutes prior to the accident. During a telephone interview, the pilot reported that while turning from downwind to base leg for landing on runway 25, the engine surged, coughed, then quit. The pilot attempted unsuccessfully to restart the engine by adjusting the throttle and mixture control, and rocking the wings. Unable to reach the runway, the pilot initiated a forced landing to an open marshy field. The aircraft landed about 1/4 mile short of the airport and nosed over during the landing roll. The right wing and the right side lift strut were substantially damaged. The pilot reported that the aircraft had accumulated a total flight time of 42.2 hours at the time of the accident. The last annual inspection was accomplished on October 14, 2001, and the aircraft had flown .7 hours since the inspection. The pilot stated that since it had been awhile since the aircraft was flown, during the pre-flight inspection, he checked and drained the fuel system at the low point as well as at the gascolator. The engine was started and ran for about 15 minutes, the pilot switched fuel tanks to ensure fuel flow, and checked the magnetos and carburetor heat prior to takeoff. A Federal Aviation Administration Inspector from the Seattle, Washington, Flight Standards District Office, inspected the engine and reported "Inspection of the engine found compression, spark, and fuel flow to the carburetor, with normal resistance noted during rotation of the engine, and no unusual noises." The fuel system strainer was inspected and found free of contaminants. Fuel flow was noted to the strainer. The top spark plugs displayed normal to rich combustion deposits. One discrepancy was noted regarding the installation of the attaching hardware for the carburetor mixture control, in that the associated castellated nut did not have a cotter pin installed, and was found loose. The lever could be moved by hand at the carburetor without movement of the control cable. However, normal movement of the mixture control arm was noted by actuation of the mixture control cable in the cockpit. The inspector reported that during a conversation with the pilot regarding the weather, the pilot initially reported the weather was 50 degrees and clear. Later, when asked about the use of carburetor heat, the pilot reported "I heard there was ice in the surrounding area, and applied carb heat." Weather obtained from Hoquiam, Washington, located 20 nautical miles west of the accident site, reported at 1622, a temperature of 45 degrees F, and dew point of 37 degrees F. The attached carburetor icing chart indicates conditions favorable for serious icing at cruise or climb power.