How does a boat spedomoter work?

[denniston]

Can anyone tell me how a boat spedo works? Is it contingent on having the original prop?

 

[scotiany]

Re: How does a boat spedomoter work?

I believe it has more to do with the boat and the current of the water you're in. I had one back in the '70s. It was inaccurate and troublesome. Get yourself a GPS.

 

[kcole683]

Re: How does a boat spedomoter work?

Water pressure.....how hard the water pushes against the pitot tube under the boat moves the gauge.<br /><br />Not very accurate in my book.

 

[Spidybot]

Re: How does a boat spedomoter work?

Or by a paddle wheel, spinning by the water passing. Transmits pulses to the instrument and is quite accurate once calibrated.<br /><br />It measures speed through water (will show a higher speed going against current).<br />A GPS device shows speed over ground and works alone on satellite signals (on most, all results are calculated from position tracking calcuations).