| 摘要 |
An odometer for boats consisting of a counter driven by an electric motor of variable speed, and apparatus for varying the speed of the motor in closely proportional relation to the speed of the boat. The motor may be of a type the speed of which is variable by changing the voltage of its operating circuit, and an electrical system may adjust this voltage by means of a variable rheostat operated by a pressure-sensitive device responsive to fluid pressure generated by forward movement of the boat in a passage opening forwardly adjacent the boat hull.
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