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  1. #1
    matthewkylelewis's Avatar
    Join Date
    Jul 2013

    quick question about speedometer speed vs GPS speed

    Hey guys, I tried to search this so if there is a thread I guess I just missed it. On some of the speed/mod threads I see that people post their GPS speed along with the speedometer speed and they are always off by a decent amount. What is the reason for this? is it impossible to make an accurate speedometer apart from GPS? My 05 fxho used to read 58/59 on glassy river water so i guess its fair to say it was really only going around 50 right? all input appreciated. thanks

  2. #2
    superair's Avatar
    Join Date
    Aug 2008
    Smith Lake, Alabama
    I believe the problem is the air and turbulence under the craft causing the paddle wheel to not stay consistent. Also same problem with ski boats. They mostly all are GPS controlled speed meters now as well. As far as the speed difference I don't know. It will be linear. So the slower the speed the more accurate it is.

  3. #3

    Join Date
    Aug 2006
    It varies with the boat, amount to debris on paddle wheel, ect. My GPR speedo read almost right on the money most of the time, but the XLT read about 8 mph high on top. The angle of the rideplate, amount of trim, weight of the rider all play a part in how water hits the paddle wheel. No way to make a paddle wheel type speedo accurate at all conditions.

  4. #4

    Join Date
    Mar 2015
    Albemarle Sound
    While the speedometer on a lot of boats tend to be not very accurate (water pressures units do pretty well) there is another factor to consider. IF the speedo and GPS were exact under ideal conditions speed over water using the boat speedo is also running in currents, upstream, downstream and would be off by the water speed as well.

  5. #5
    dockwalker's Avatar
    Join Date
    Mar 2010
    On the water near Belhaven,NC
    Google CanDoo Speedometer.Gps hookup for OEM dreamometer.

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