The failure of the pilot to maintain airplane control after experiencing a loss of power from the left engine due to water contamination of the fuel system. Contributing to the accident was the pilot’s inadequate preflight inspection of the airplane and maintenance personnel’s inadequate annual inspection, because both failed to detect the long-term water contamination of the fuel system and the deteriorated outer o-rings on both fuel caps. Also contributing to the water contamination of the fuel system was the inaccurate information and instructions in the airplane maintenance manual pertaining to overhaul requirements of the fuel filler caps.