On June 15, 2003, at 1338 eastern daylight time, an Enstrom 280C, N5695D, owned and piloted by a commercial pilot, sustained substantial damage when it impacted water following a loss of engine power near West Branch, Michigan. Visual meteorological conditions prevailed at the time of the accident. The pilot reported serious injuries and his passenger reported no injuries. The 14 CFR Part 91 personal flight was not operating on a flight plan. The flight departed from a private helipad near West Branch, Michigan, at 1320 with an intended destination of Selkirk, Michigan. The pilot reported he did not notice any anomalies with the engine gauges while in hover shortly after liftoff. The pilot noted he was in a climbing departure when he heard noises over his headset. The pilot stated he did not have enough engine power to continue flight, so he began an autorotation. The pilot reported he steered right during the autorotation and landed upright about 75 feet off the shore in about 2-1/2 feet of water. A Federal Aviation Administration (FAA) airworthiness inspector conducted the on-scene inspection of the helicopter. The inspection of the helicopter confirmed flight control continuity. Both fuel tanks contained 25 gallons of fuel and the engine contained 8 quarts of oil. The main and tail rotors showed drivetrain continuity. A large hole was found in the crankcase, near the number one engine cylinder, and the number one connecting rod was protruding from the hole. Examination of the broken connecting rod cap revealed fracture features that were consistent with a fatigue-type failure. Additionally, the material encompassing the fatigue initiation point was galled along with several other areas of the bearing interface.