Differential bucket control system for waterjet boats

A boat of the type driven by at least two waterjets, the boat comprising:

• at least two waterjet drive assemblies, each assembly comprising:
• a nozzle at the stern of the boat, the nozzle directing a flow of water generally along the longitudinal direction, the nozzle being capable of rotation about a generally vertical axis to provide left and right sideward forces on the stern;
• a reversing bucket for reversing the direction of a variable amount of the flow of water emerging from the nozzle, the reversing bucket being adjustable from any of a plurality of forward thrust positions in which enough water remains sufficiently unaffected by the reversing bucket that a net forward thrust is maintained, to a neutral thrust position in which a substantial fraction of the flow of water is reversed so that the net thrust of the water reversed and the water not reversed is approximately zero, to any of a plurality of reverse thrust positions in which enough water is reversed that a net reverse thrust is maintained;
• actuators for producing movement of the nozzles and reversing buckets;
• a control circuit for controlling the actuators
• the control circuit, actuators, and waterjet drive assemblies being configured to provide three types of movements of the nozzles and reversing buckets:
• (1) movement of the buckets in unison, to produce the forward and reserve thrust;
• (2) rotation of the nozzles in unison to provide the left and right sideward forces on the stern, (3) differential movement of the buckets, to produce a torque about a generally vertical axis to move the bow of the boat to the left or right;
• and
• a joystick device connected electrically to the control circuit, and configured to control movement of the reversing buckets in unison, rotation of the nozzles in unison, and differential movement of the buckets.