On March 6, 2005, about 1346 central standard time, a 1973 Cessna 177RG, N2019Q, owned and piloted by a private pilot, sustained substantial damage during a forced landing following a loss of engine power while maneuvering near Rochester Minnesota. The 14 CFR Part 91 personal flight was operating in visual meteorological conditions without a flight plan. The passenger received serious injuries and the pilot received minor injuries. The local flight originated about 1330. The pilot reported that on the accident flight he checked the oil pressure before takeoff and during the flight. He said that the last time he checked the oil pressure was about 3 to 4 minutes prior to the engine failure. He stated that after over flying his residence the engine began to vibrate "fiercely" and then seized as he attempted to reduce power. The pilot stated that he attempted to land on a local highway and the right wing struck a tree during the landing. The pilot stated that the airplane then came to rest in a field adjacent to the runway. The pilot reported that an annual inspection had just been completed on the airplane. He stated that he and his son assisted the mechanic by operating the engine while the mechanic checked for leaks. The pilot reported that no leaks were found. Examination of the airplane's engine subsequent to the accident revealed an oil leak that was traced to the propeller governor mounting pad. The propeller governor mounting nuts were found to be torqued slightly more than finger tight. The aircraft maintenance manual specifies a torque range of 100 to 150 inch pounds of torque for the mounting nuts. In addition, it was found that there were only 3 lock washers and 2 flat washers distributed between the 4 mounting nuts. Further examination of the propeller governor installation revealed a single gasket between the propeller governor and the engine accessory case. The maintenance manual for Cessna 177 airplanes produced between 1971 and 1975 indicated the use of a single gasket during installation of the propeller governor. The maintenance manual for Cessna 177 airplanes produced between 1976 and 1978 indicated the use of 2 gaskets separated by a plate in accordance with Lycoming Service Instruction 1438 or the latest revision. Additionally, Lycoming Service Instruction 1438 stated that the use of 2 gaskets separated by a plate are necessary "to eliminate the possibility of oil leakage between the propeller governor and the accessory housing." Further examination of the engine revealed that the oil level was below the bottom of the oil dipstick and that the number 4 connecting rod was broken. According to maintenance records, the date of the annual inspection was March 2, 2005. The maintenance records indicated that the propeller governor was removed, overhauled, and reinstalled during the annual inspection.