| 摘要 |
A speed measuring device for use with shallow draft jet pump propelled boat is disclosed. The device which includes a magnetized paddle wheel with diametrically opposed paddles having similar charges and adjacent paddles having opposite charges, is mounted in a housing adjacent a "hall-effect" device which translates the rate of rotation of the paddle wheel into a speed measurement reading due to the changes in the frequency of changes in the electrical field produced by rotation. The present invention is different from all other speed measuring devices in that the paddles do not protrude beyond the surface of the hull of the watercraft and therefore cannot become damaged by sand, rocks, or other floating debris. The invention includes a substantially flat base plate with a progressive recess on the underside thereof. This progressive recess carries water to a cavity or housing within which the paddle wheel is rotatably mounted.
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