On January 8, 1995, about 1653 eastern standard time, a Mooney 20J, N205MD, registered to Steven Miller, operating as a 14 CFR Part 91 personal flight, experienced a loss of oil pressure in cruise flight, and made a forced landing into Tampa Bay. Visual meteorological conditions prevailed and no flight plan was filed for the local flight. The airplane sustained substantial damage and the private pilot and two passengers reported minor injuries. The flight originated from St. Petersburg, Florida, about 4 minutes before the accident. The pilot stated he taxied the airplane to a fixed-base operator for fuel, and completed a preflight inspection of the airplane. When checking the oil, he noticed the oil cap was crossthreaded. The dip stick indicated close to 8 quarts of oil. He taxied to runway 35 and was cleared for takeoff. On climb out the control tower informed him that the airplane was trailing smoke. He informed the tower that the airplane had just had an oil change, and that it should burn off. When he leveled the airplane at 1,000 feet msl, the engine was running rough, and the oil pressure was decreasing. He informed St. Petersburg tower of the situation and informed them that he was returning to the airport. The tower asked if he required any assistance, and cleared him to land. When he reduced power, the engine began to shake violently, and a forced landing was made into Tampa Bay. Examination of the engine assembly and accessories was conducted by personnel from Textron Lycoming in the presence of the FAA. Disassembly of the engine revealed a separation of the No. 3 rod cap and rod bolts. The crankshaft rod bearing journal exhibited black discoloration and the rod bearings were extruded. The components were forwarded to the NTSB Materials Laboratory for analysis. (For additional information see, Textron Lycoming Accident Investigation Report). Examination of the No. 3 connecting rod bolts revealed they had separated in two pieces. The pieces contained bending and necking down deformation and a rough fracture surface, typical of an overstress bending separation. The crankshaft ends of the connecting rods, the connecting rod journals, and the nearby portions of the crankcheeks were darkly discolored as if severely overheated. (For additional information see, NTSB Metallurgist's Factual Report No. 95-100). The components were released to Mr. Les Waters, on May 22, 1995.