RedactedNarrative: Vessel 1, a 39ft Contender open motor vessel bearing FL 4387 RJ, was executing a turn to starboard. According to statements provided by Operator 1, he was operating the 39ft Contender with 4 400hp outboard motors at a speed of 40mph when he conducted a turn to starboard. Operator 1 stated that when he turned his vessel to starboard to execute a J-Turn that he lost control of his vessel. Operator 1 stated that the vessel rocked from side to side and he felt that he was to be ejected and slammed the throttles into reverse to cut the engines. Operator 1 stated that he was ejected from his vessel and that the gunwale of the vessel slammed into the water causing damage to the vessel. Operator 1 was recovered from the water and taken to the Hospital as a precautionary measure; the vessel was taken to Miami Beach Marina and put on a vessel lift. Operator 1 stated that wind and sea conditions were calm at the time of the accident. It is determined that the cause of the accident was due to Operator 1 conducting a turn at an unsafe speed resulting in a type of high-speed instability. Operator 1 was cited for careless operation of a vessel resulting in an accident. Operator 1 was also provided with case information. Vessel FL 4387 RJ was photographed, and damage documented at Miami Beach Marina.