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→Design Considerations
Other industries take different approaches. Racing cars have long used flexible Constant Velocity (CV) joints, with engines of over 1000 hp. Tractors use flexible drive shafts running from a power-take-off (PTO) on the back. These shafts are extensible on splines, and use universal joints for alignment. There is little direct loading on the PTO bearings. Some vehicles also use a fully hydraulic transmission and drive.
These advantages can be obtained in a boat by using a hard-mounted thrust bearing to take the shaft thrust from the propeller, and flexibly coupling and mounting the engine.
Boats are retro because: (1) tradition; (2) hard fixed mounts are cheaper; (3) simpler is better (more reliable); and (4) tradition (i.e., mistrust of unknown technologies). All of the alternatives are more complicated, which is not what you want with a breakdown in a crisis.
