A steering system for a ski boat having a helm, a propulsion motor, a propeller, and a rotatable propeller shaft, said helm being adapted for input of operator commands for speed and steering, said propeller being mounted on said rotatable propeller shaft, said propeller shaft being linked to transfer power directly or indirectly from said propulsion motor to said propeller, and said propeller being positioned to be in a flow of water supporting said ski boat when said ski boat is moving relative to the water, comprising:
- a. a pair of rudders operatively mounted to interact with said flow of water;
- b. said pair of rudders including a movable aft rudder operatively mounted to interact with said flow of water aftward of said propeller;
- c. a movable forward rudder operatively mounted to interact with said flow of water forward of said propeller;
- and
- d. a rudder control system including controls that operatively move one of said pair of rudders without moving the other of said pair of rudders when the ski boat is traveling in a first range of speed conditions;
- and
- e. said rudder control system also including controls that operatively move both of said pair of rudders, thereby achieving greater exposure of rudder turning surfaces to said water flow, when the ski boat is traveling in a second range of speed conditions
- f. an aft rudder steering shaft attached to said aft rudder, the rotational axis of said aft rudder steering shaft positioned aft of said non-steerable propeller and approximately intersecting along the extended centerline of said propeller shaft;
- g. an aft rudder controller in communication with, and capable of controlling the pivotal movement of said aft rudder steering shaft and thereby changing the angle of said aft rudder in relation to the longitudinal centerline of said propeller shaft such that when said helm is commanded to starboard an operating body portion of said aft rudder rotates to starboard and when said helm is commanded to port said operating body portion of said aft rudder rotates to port;
- h. an aft rudder angle sensor for detecting and transmitting a relative rotational position of said aft rudder steering shaft;
- i. a helm sensor transmitting said helm's command to said aft rudder controller;
- j. a throttle control to command the speed and thrust direction of said non-steerable propeller;
- k. a throttle control sensor detecting and transmitting said throttle control's speed and thrust direction commands;
- l. a strut securing said propeller shaft to said hull of said ski boat;
- m. said movable forward rudder located generally aft of said strut and forward of said non-steerable propeller;
- n. a forward rudder steering shaft attached to said forward rudder, the rotational axis of said forward rudder steering shaft positioned forward of said non-steerable propeller and along the longitudinal centerline of said propeller shaft;
- o. a forward rudder controller capable of controlling the movement of said forward rudder steering shaft and thereby changing the angle of said forward rudder in relation to the longitudinal centerline of said propeller shaft;
- p. an electronic controller receiving input information from said helm sensor, said throttle control sensor, and said aft rudder angle sensor, said electronic controller including a control signal generator;
- q. said control signal generator sending control signals to said forward rudder controller based on said input information, said control signals transmitted to said forward rudder controller to rotate said forward rudder steering shaft and thereby change the angle of said forward rudder in relation to the longitudinal centerline of said propeller shaft, such that:
- (1) when said throttle control commands a forward or no thrust, said forward rudder remains aligned parallel to the longitudinal centerline of said propeller shaft;
- (2) when said throttle control commands a reverse thrust and said helm is selected to starboard, said forward rudder rotates to port in direct proportion to the aft rudder rotation to starboard;
- (3) when said throttle control commands a reverse movement and said helm is selected to port, said forward rudder rotates to starboard in direct proportion to the aft rudder rotation to port.