US Patent 7666040 Watercraft swivel drives

Enhanced watercraft performance is provided by combinations of one or more inboard swivel propulsion drives and hull tunnels. A tunnel at the hull centerline with specific features provides performance advantages for a center swivel propulsion drive. Use of front propeller based traction propulsion is particularly advantageous in the swivel drive systems and allows the use of tunnels with improved tunnel conformations. Advantages of the traction swivel drive arrangements include minimization of hull space with smaller engine room volume, greater propulsion efficiency and improved watercraft handling.