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C-120 speed reading.

Old 07-17-2005, 10:41 AM
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Default C-120 speed reading.

I recently have taken delivery of a Sailfish 2660 with a Raymarine C-120. For some reason the speed reading from the transducer is reading about 5-10 MPH less than the GPS. In addition, the yamaha guages reads teh same as the GPS. Any suggesytions on how to fix this problem?

Old 07-17-2005, 07:15 PM
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Default Re: C-120 speed reading.

I'm confused. You want SOG I believe, speed over ground.

The yamaha gauge has nothing in common with the transducer, its' speed comes from some sensor in the lower unit and isn't very accurate (I think). It's late and I'm tired, but I'm pretty sure the Yamaha gauge is showing a speed unrelated to the transducer. You'll note when heading into a current it will read a few MPH faster than the GPS. You can have the C120 pull the speed off the wheel on your transducer, but it will suffer from the same problems as the Yamaha speedo.

Where are you boating? If you are running with a current, your Yamaha gauge will misrepresent the speed by a fair a 5mph current about 5mph over reality, which is your true speed over ground.

Flip through the manual and take a look at the databar section. What you want up there is SOG...this is driven off the GPS within the unit.

Old 07-18-2005, 08:20 PM
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Default Re: C-120 speed reading.

There is a setting change you can do to "calibrate" that paddlewheel. Why would you want to do that? You can anchor in a current and go 10mph with that stupid thing. Trash that speed as it's just not reliable. Use the SOG from the gps. I have a Sailfish 266 with a RayMarine C80. The Yamaha speed gauge is usually close to correct. I think it's based on the vacuum in a tube that goes into a lower unit. It will probably plug and be unreliable. SOG on the gps. Forget the rest.
Old 07-19-2005, 09:00 AM
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Default Re: C-120 speed reading.

I would use the speed from your GPS instead of the paddle wheel on the ducer. The paddle wheel is about the most inaccurate device in the system.

The paddle wheel will help for you to know the water current speed. BUt for boat speed use the GPS on the C-120.


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