| 摘要 |
<p>A marine propulsion unit comprises a cowl (10), a propeller shaft (4) mounted on the cowl, and a propeller mounted on the propeller shaft. The propulsion unit can be mounted on a boat simply by attaching the cowl (10) to the hull of the boat (1). To avoid increasing the draught of the boat, the underside of the hull can be provided with a recess 2, so that the propeller (3) is received in the recess (2) when the propulsion unit is fitted to the boat. The propulsion unit may also include a blade (7) mounted downstream of the propeller (3). Rotating the blade about a substantially vertical axis deflects the thrust generated by the propeller (3) so as to steer the boat to which the propulsion unit is applied. The boat (1) can be provided with means (20) for directing air towards the propeller (3) of the boat. Directing air towards the propeller (3) promotes cavitation at the propeller thereby reducing the drag exerted by the water on the propeller. In consequence, the propeller is able to rotate faster for a given torque, and thus provides a greater power output.</p> |
