At about 13:30 EST, a Mooney Ovation lost power and landed at Marathon Airport. The airplane was not damaged in the landing and no one was injured. The flight originated at 13:10 from Fort Lauderdale Executive Airport and was en route to Key West. The flight was at a cruise altitude of 6,500 feet, with the power set at 2,400 rpm and the manifold pressure at 24 inches, when the engine surged twice, then started to vibrate. The vibration stopped for a moment then started again. Oil covered the windshield and smoke started coming from the engine. The Continental IO-550 engine had a total of 103.2 hours since new, and preliminary indications are that the engines crankshaft failed.