On January 20, 1994, about 2018 eastern standard time, a Cessna 152, N68411, registered to Cecily's Flight Center, Inc., was substantially damaged during a forced landing near Osprey, Florida, while on a 14 CFR Part 91 instructional flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The certified flight instructor (CFI) and student were not injured. The flight originated from the Venice Municipal Airport, Venice, Florida, about 10 minutes earlier. The CFI stated that the flight originated from the Albert Whitted Airport, St. Petersburg, Florida, about 1910, and flew to the Venice Municipal airport where the student performed four touch-and-go landings. The flight departed the traffic pattern to return to the departure airport, climbed to 2,500 feet mean sea level and obtained VFR flight following with Tampa Approach Control. During cruise flight the engine rpm dropped 300-400 rpm then the engine quit and the propeller stopped. The CFI took control of the airplane and at 2016.23, told Tampa Approach Control "Cessna 68411 Mayday Mayday Mayday we have uh engine failure attempting a forced landing on." The approach controller did not respond and continued issuing ATC instructions to 2 aircraft. At 2117.08 the pilot of one of aircraft (N84476) responded "0404 76 did you copy that mayday." At 2117.11, the approach controller stated "November 411 say again." The pilot of N68411 repeated the Mayday call, advised of an engine failure and stated that he would be attempting a forced landing along the coast line. Due to people on the beach the pilot elected to land just offshore and after touchdown, the airplane went inverted. Both occupants exited the airplane, walked to shore, and were assisted by the bystanders. The engine was removed for further examination. Examination of the engine revealed that the crankshaft failed at the No. 4 crankcheek between the aft radius of the No. 2 main journal and the forward radius of the No. 3 rod journal. The crankshaft was examined by the NTSB metallurgy department. Metallurgical examination of the fracture surfaces of the failed crankshaft revealed that it failed due to high cycle fatigue which emanated from multiple origins along the aft radius of the No. 2 main journal. Circumferential gouge marks were observed along the aft radius of the No. 2 main journal. X-ray spectrum of the gouge marks indicate that elements of lead and copper were observed. According to a representative of the engine manufacturer, bearings are comprised of in part, lead and copper. Review of the engine logbooks revealed that the engine was overhauled on December 5, 1986. The engine had accumulated at that time 2,079 hours. At the time of the accident the engine had accumulated a total of 4143.7 hours, which is about 2,065 hours since the overhaul in 1986.