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Old 26 January 2019, 11:41   #1
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Garmin Echo 551dv Calibration

Hi, I wonder if anyone can tell me why my Echo 551dv is showing 2.5ft depth when I tested it in 12" of water in a bucket? The keel offset is set to zero in the calibration settings. When I select 200kHz or DownVu the situation is even worse showing 6.5ft depth with fish.

Do I need to get a new transducer? If so what is the best one to buy? I was thinking of upgrading anyway. Or should I get a complete package?

It's quite important to me as I don't really care if I'm in 50ft or 150ft of water at sea, but in the upstream murky waters of a tidal river it's critical.

Many thanks!
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Old 26 January 2019, 12:03   #2
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Did you change the garmin from salt to fresh water in settings?

You will need a keel offset of some kind, looks about 8" in that picture?

That is a decent plotter, if it is a good transducer it will just be settings.

However, if you want to upgrade I'll buy that 551 from you. I'm about to spray my 551s to black.
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Old 26 January 2019, 12:29   #3
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Fresh or Salt is a setting I didn't know about and didn't find.

https://youtu.be/85D9auYUNsY

You are right about the offset but if the unit was reading correctly I would avoid being in less than 12" of water without tilting the engine.

Scary thought that I was on the Tamar last year going quite briskly believing I was in 3.9ft of water when it might only have been 1.5ft with 8" of that taken by the prop.
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Old 27 January 2019, 09:18   #4
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you'll get a false eco in the bucket because it will shoot through the bottom plastic i found my garmin 551 not particularly accurate in very shallow water i just set mine with a 1 m alarm keeps me out of bother unless you have a lone rock sticking up
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Old 27 January 2019, 14:49   #5
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I agree with Jeff. Something tells me you can't calibrate them in a small body of water like a bucket etc. I calibrated mine at anchor in shallow water over a firm sand seabed. I used an Engineers survey staff (could of used a stiff tape measure etc instead) to measure from the transducer to seabed and tip of skeg to seabed and set the offset as appropriate.

One unit gives me actual water depth from surface and one gives me clear water depth below the skeg on the engine (fully trimmed down) which is the deepest point on the boat. Either way for normal navigation etc I like to ensure there's a couple of metres under the boat at least!
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Old 27 January 2019, 16:42   #6
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One cannot calibrate an echo sounder in a bucket, as the signal bounces around inside the bucket, reflecting off the side and bottom of the bucket giving the wrong depth due to the path it has taken through the water.
In my experience, echo sounders are very inaccurate in less than 2m of depth. However, if you set the alarm depth at 2m it will give you a good warning as you are approaching a shallow.
I have calibrated my echo sounders by dropping a rope over the side, with a weight (a lead line) and when it touches the bottom pull it in and measure the wet length. Then adjust the measurement for the hull depth etc.....
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