1. Field of the Inventions
The present inventions relate to boats that can be steered by pivoting a steering nozzle in accordance with an operation of a steering handle unit.
2. Description of the Related Art
The heading of boats, such as jet-powered type boats, can be changed at the desire of the operator by the movement of a steering handle unit on the watercraft. For example, a personal watercraft is one of these types of boat. Personal watercraft typically also have a throttle lever adjacent to a grip of the steering handle unit. The throttle lever is used to control the power output of the engine.
The engine of a jet type boat drives a jet pump which draws water in and discharges the water rearwardly to generate a propulsion force. A steering nozzle is disposed at a rear end of the jet pump. In accordance with the operation of the steering handle unit, the steering nozzle pivots to change a direction of the water discharged from the jet pump. The traveling direction of the vehicle body thus can be changed.
A conventional steering pump for a personal watercraft such as that described above, has a push-pull cable connecting the steering handle unit with the steering nozzle. More particularly, the steering nozzle is disposed at the nozzle opening of the jet pump and is mounted for pivotal movement about a vertical axis. When the push-pull cable is pushed or pulled in accordance with the operation of the steering handle unit, the steering nozzle is directed rightward or leftward in a generally horizontal plane. Because the steering handle unit and the steering nozzle are directly connected to each other through the push-pull cable, in the conventional personal watercraft, the steering ratio (which is a ratio of a steered angle of the steering nozzle relative to a steering angle of the steering angle) is constant over the entire range of movement, regardless of the speed of the personal watercraft.
The water jet passing through the steering nozzle in an upper speed range of operation can be more powerful than under other conditions. Because of the difference in the force resulting from a higher speed water jet in contrast to a lower speed water jet, and because of the direct connection through the push-pull cable, the steering loads during operation at higher speeds and lower speeds are inevitably different from each other.
In addition, the push-pull cable systems extending between the steering handle unit and the steering nozzle cannot be bent around sharp corners, which thus requires special routing and the allocation of more space for routing of these cable or cables. In other words, the push-pull cable needs to be laid as straightly as possible. If the push-pull cable is laid under a preferable, non-bent condition, the space available for positioning other devices or components becomes limited. Thus, the use of push-pull cables makes it more difficult to effectively use the space inside of an engine room of a boat.