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Sonar / Fishfinder no workie

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  • Sonar / Fishfinder no workie

    Howdy from a year long or so lurker. All the great info here is awesome, particularly now that I have a question that hopefully someone can help me with. I recently replaced my separate GPS and Fishfinder units with a single unit, the components of which include a Garmin 3006c GPSmap/chartplotter, the corresponding GPS 17N antenna, a GSD 21 sonar module, and the corresponding transducer. Everything works great except the sonar/fishfinder. The first time out it worked fine up until I was cruising at about 14kts heading up Derickson Bay in what the chart indicated was 400'+ of water when the depth reading went to 24'. I slowed and eventually came to a complete stop to get an accurate reading but after that I could not. The next time the sonar seemed to work right was back in the small boat harbor at Whittier. Every time out since then I get good readings in the harbor until I exceed 7 kts or so, then it flashes with inaccurate readings. I expect that when moving along, but once upset the sonar will not read accurately even if at a crawl or stopped. I've tried turning off the motor, resetting all of the electronics, adjusting all of the settings, pretty much everything I can think of short of replacing parts. The Garmin tech line has been zero help so far. Anyone have similar issues? Any thoughts, ideas fixes would be much appreciated. BTW great weather in PWS last week, the shrimp were tasty too!
    Two men say they're Jesus, one of them must be wrong...

  • #2
    I can think of three things that would cause this and they all have to do with transducer postion.
    1. Transducer isn't postioned low enough in the water.
    2. Getting bubbles around the transducer.
    3. Transducer is tilted wrong. In deep water if bottom of transducer is level with bottom of boat (while sitting still) it will read more horizontal thru the water due to bow coming up when underway.
    Is transducer a 50/200 dual frequency? I've noticed with some dual freq. transducer they need to be set on dual to read correctly.
    Just a few thoughts...


    • #3
      You've already done this but...make sure you are set for the depth you are running in. Learned the hard way with mine. Also, make sure that your transducer is still locked in it's cradle. I hit a huge wave last weekend and it popped it out of the bracket. Didn't find out until we took the boat out of the water. Good luck!


      • #4
        I have an old Humminbird Wide Onehundred that is still on my boat. I have never been able to get it to work corectly at plane speeds.

        I just replaced with a Garmin 498C. We will se how it works.


        • #5
          Getting your FF to read at planing speed may take lots of small adjustments, I made a 4x6 inch mounting bracket for mine and it has 6 sets of mounting holes in it from repositioning it. Mine now reads good up to 30 mph, started fading 10 mph when I started. First thing to do is look under boat and try to stay away from any ribs on bottom and anywhere the bottom is concave as air bubbles travel fron front to rear in these areas. Mount the pick-up about 2/3 up from bottom if its a V-type bottom. You can try it horizontal, but I find it will work better angled down slightly in the rear (this will help at higher speeds) bottom of pick-up must be below bottom of boat and level side to side. Its a pain but move it a little each time you get back on the trailer to see if its better (mark with a Sharpie each location) Good Luck
          Alaska Wildrose Charters and Cabins


          • #6
            Garmin trouble

            I have a Garmin 188c on my boat. It worked fine 1st time, then was schitzo after that. I called help line, with no luck. finally sent the whole unit in to garmin. they said, somehow my unit software had become corrupted and the transducer had also failed. They replaced the transducer and reformatted the unit. no questions from them and they paid shipping.


            • #7
              Still trying stuff

              Thanks to all for the inputs. I've still been unable to get the stupid thing to work. I might try replacing the transducer next. Onthefrinj, did that fix the problem for you?
              Two men say they're Jesus, one of them must be wrong...


              • #8

                Mine did the same thing, under 30-40ft it reads great at any speed. The Garmin people at the sportsman show said at or about 18 mph on up and in deep water the signal on the sonar cant reach the bottom and return before your boat has moved out of the zone. Hope this helps i use a Garmin 238 GPS/Sounder call garmine and check it out. Good Luck!!


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