On March 15, 2001, at 1200 eastern standard time, a Cessna 182B, N2502G, collided with the ground and nosed over during an off-airport emergency landing to a field near Boynton Beach, Florida. The personal flight was operated by the pilot under the provisions of Title 14 CFR Part 91 with no flight plan filed. Visual weather conditions prevailed at the time of the accident. The airplane received substantial damage. The commercial pilot and his passenger sustained minor injuries. The flight departed Palm Beach County Park in Lantana, Florida, at 1150. A few minutes into the cruise portion of the flight, the pilot heard a 'loud bang' and the engine began to vibrate violently. The pilot immediately reduced engine power and checked the flight controls and determined that they were operational. The engine continued to vibrate it reduced engine power and would not respond when the throttle was advanced. The pilot selected the only available open area and attempted an emergency landing. During the landing roll, the airplane collided with a two foot berm and the nose wheel assembly collapsed. After the nose wheel assembly collapsed, the airplane skidded about 200 feet and nosed over. Examination of the airplane revealed an actuator pin on one of the propeller blades had failed, and the pilot was unable to control the propeller blade pitch from the propeller control lever in the cockpit. A review of maintenance records revealed the failure occurred 205 hours before time between overhaul. The maintenance records also disclosed that the McCauley propeller assembly, model number 2A36C29, S/N581501, was returned to service after a complete overhaul on May 1, 1990. Subsequent to the overhaul, the maintenance logs showed several leading edge repairs to the propeller blades. No repair station records of the maintenance were recovered. A review of recent service difficulty data failed to disclose a history of actuator pin failure with this propeller model.