On August 17, 2018, about 1320 eastern daylight time, a Beech N35, N1330Z, sustained substantial damage when it was involved in an accident near Mayport, Florida. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The flight departed Rutherford County Airport (FQD), Rutherfordton, North Carolina, about 0930 and was destined for Ormond Beach Municipal Airport (OMN), Ormond Beach, Florida. The pilot reported that he was in cruise flight with the airplane at an altitude of 4,500 ft when the engine lost total power. The pilot's attempts to restart the engine were unsuccessful. He contacted air traffic control and was advised that Mayport Naval Station (NRB), Mayport, Florida, was the closet airport to his current location. The pilot responded that he was unable to make it to the airport and ditched the airplane into the Atlantic Ocean, about 3 miles east of NRB. The crew of a nearby ship rescued the pilot. Postaccident examination of the airplane after recovery revealed that both elevators were separated from the horizontal stabilizers. Due to the saltwater immersion, the continuity of the engine’s valvetrain and powertrain could not be established. Visual examination of the engine revealed that a fuel line that had been attached to the fuel flow sensor was broken; the fuel flow sensor and the broken fuel line were removed and sent to the National Transportation Safety Board Materials Laboratory for further examination. Examination of the fracture surfaces on the broken fuel line revealed the features were consistent with high-stress, low-cycle fatigue crack propagation. The crack initiated at the outside, progressing through the thickness of the aluminum fuel line and partially along its circumference until final overstress fracture. A review of the installation drawings and instructions revealed that the fuel flow sensor was installed without a mounting bracket per Insight drawing 1000-303 (bracket type 3), which depicts installation using a metal plumbing fitting for support directly to the engine fuel distributor. Insight drawing 1000-303 (bracket type 1) depicts the fuel sensor attached to the engine top case bolts and the fuel flow sensor plumbed with flexible hoses, and Insight drawing 1000-303 (bracket type 2) depicts the fuel sensor attached to the firewall and the fuel flow sensor plumbed with flexible hoses. The Insight Avionics installation manual states that the installing mechanic should determine which type of mounting is best for their installation, as all three types are approved. A review of the maintenance logbook entries revealed no record of the fuel flow sensor installation. However, an Insight G-2 installation record dated January 18, 2016, indicated that the Insight G-2 engine monitor was installed with six exhaust gas and six cylinder head temperature probes only.