| 摘要 |
An elongated support is either mounted or hand-held on a small boat so as to slant downwardly from the hull toward the water. A speedometer head at the upper end of the support is driven by a shaft rotatably journalled on the support. The free lower end portion of the shaft extends beyond the lower end of the support into the water and carries an impeller which is rotated by movement of the boat through water. The shaft is normally straight but its lower end portion is resiliently flexible in all directions so that the axis of rotation of the impeller is aligned with the water slipstream and drag is materially reduced.
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