Steering mechanism for small boat having multiple propulsion units

1. A small boat comprising a steering wheel, a steering angle sensor adapted to detect a steering angle of the steering wheel, a plurality of propulsion units mounted to a transom of the boat, each of the plurality of propulsion units coupled to an electrically operable steering device, and a control unit adapted to independently control an output of each of the plurality of propulsion units, wherein the control unit adjusts the output, a trim angle or a height of a propeller of each of the plurality of propulsion units in accordance with the detected steering angle and a running condition of the boat such that a total thrust of the plurality of propulsion units and running direction of each of the plurality of propulsion units can be used to effect turning operations of the boat and wherein, upon detection of a malfunction of at least one of the electrically operable steering devices, the control unit further is adapted to set a turning angle to a preset angle and to adjust the output of each of the propulsion units based upon the steering angle of the steering wheel such that the running direction is based upon a difference between the respective outputs.

2. The small boat according to claim 1 , wherein the output of said each one of the propulsion units is adjusted using at least one of a throttle valve opening, an ignition timing characteristic, a fuel injection condition and a mode shifter condition.

3. The small boat according to claim 1 , wherein the preset angle is a turning angle that is given under a malfunction condition.

4. The small boat according to claim 1 , wherein the preset angle is a turning angle that is given when said each one of the respective propulsion units is returned to a straight-ahead position.

5. A small boat comprising a hull, a steering wheel mounted to the hull, the hull comprising a transom, a first propulsion unit and a second propulsion unit mounted to the hull generally in parallel, a steering device positioned on the small boat, the steering device adapted to cause steering movement of the first propulsion unit and the second propulsion unit, multiple sensors mounted to the small boat and providing data regarding multiple operating characteristics of the small boat, and means for controlling an output amount and output direction of the first propulsion unit and the second propulsion unit independently of each other such that the small boat can be steered at least in part by the relative output amounts and directions of the first and second propulsion units in response to movement of the steering wheel and data provided by at least one of the multiple sensors, and wherein, upon detection of a malfunction of at least one of the electrically operable steering devices, the means for controlling an output amount and output direction of the first and second propulsion units further is adapted to set a turning angle to a preset angle and to adjust the output of each of the propulsion units based upon the steering angle of the steering wheel such that the running direction is based upon a difference between the respective outputs.

6. The small boat of claim 5 , wherein the multiple sensors are selected from the group consisting of a speed sensor, an attitude sensor, a yaw rate sensor, a lateral acceleration sensor, an engine condition sensor, a shift position sensor, and an accelerator sensor.

7. The small boat of claim 5 , wherein output direction can be modified by turning at least one of the first and second propulsion units, by raising at least one of the first and second propulsion units, by trimming at least one of the first and second propulsion units, or by changing a rotational direction of an output shaft of at least one of the first and second propulsion units.