Depth sounder(fish finder) at speed?

Drew Stephens

Almost A Member
Dec 6, 2017
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Ventura, CA
Name
Drew Stephens
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Sunbird Neptune 230
Whatsups guys, got a Garmin UHD "depth sounder" "fathometer" "fish finder" whatever you wanna call it. I cant get readings when the boats on plane. Sometimes the depth will work for a second or two then its all just blank distortion. No I dont want to do a thru hull transducer either. I was just wondering you guys running transducers on your transom if you have any tips on mounting or anything that would help. Mine came mounted from the previous owner like this in the pictures.

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clevel

Skipper
  • Jun 4, 2011
    1,235
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    Laguna Niguel
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    Cabo Jack
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    Cobia 261
    Mounted too low causing turbulent water that interferes with sonar. Bottom of transducer should be level and flush with bottom of hull. Search on internet for manufacturer’s install instructions.
     
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    Unassailable

    Professional Amateur
    Aug 26, 2009
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    San Diego
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    John B
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    BW
    Holy crap, Batman! That thing is low. Best to give it a little tilt forward, too.

    Also, can't tell if that's a strake in front of it. If it is, move it about 6" towards keel. You may want to get or make a stern saver because it looks like you may need to make some adjustments and you're already going to have to seal some holes.
     
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    bman440440

    I am the one who knocks!!!
    Sep 8, 2010
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    B-MAN
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    Heisenberg(20' Maxum), Sip N' Slide (33' 2 deck w/slide) Ships & Giggles (32' double deck pontoon)
    here is how mine is mounted and I'm able to read bottom at 20+ with little interference and at 18 or below no interference

    2.jpg


    3.jpg
     
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    Croaker.Stroker

    Old White Guy
    Nov 28, 2015
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    Tustin
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    Croaker
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    Arima Sea Pacer
    Way too low. Should only extend 1/4” to 3/8” below the bottom surface of the hull.
     
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    dwaynesda

    dwayne
    Apr 27, 2003
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    The interference you see on your screen is air bubbles.You can not have any air bubbles at all going over the face of the transducer. Transducer placement is different for every boat hull and transducer combo. You have to experiment and it can be time consuming. Have someone else drive the boat while you look over the stern while underway to find the "cleanest" bubble free water. That is the area where you start your experiment.
     
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    Day0ne

    I Should Upgrade My Account
    Dec 24, 2004
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    233 Formula Shadowdancer
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    ssrmr2

    Member
    Mar 15, 2006
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    Steve
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    17' montauk "Anger Management"
    raise it up. add some 4200 to the screw holes. stern saver works wonders I have one on my sled

    different topic looks like the port outer bunk needs to be pushed out to get the boat from riding on it.
     
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    ShadowX

    I Post A Lot But I Can't Edit This
    Oct 10, 2010
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    Others have pointed out that its mounted too low. The other big no-no is to put in near the lifting strakes. Those strakes help lift the boat up, so there is a lot of turbulence underneath the flat area. You might be better off putting the transducer in one of the angled areas shown by bman440440.

    The best way to find out a good spot is to just run your boat at planing speeds in a calm area inside the harbor. Have someone take over the controls and maintain a straight heading. Now you go to the back of the boat and observe the water underneath the boat. If the water flows clear, it means it has low turbulence. If the water is white and frothy, it has a lot of turbulence. Once you find a good spot with clean water, mark it on the boat so you can install the transducer when you get out of the water.

    If you mount it on the angled area, the side near the engine is about flush to the boat line. You might want to have it slightly above the edge. The transducer should be mounted parallel to the water line as best you can. You may need to make adjustments later. Start with the transducer parallel as shown below. If you still see turbulence, angle down the end one notch, but don't go apeshit on the angle and have it crab into the water too much or you will generate a roostertail. Most of the time, you don't need to angle it because the boat naturally lifts the bow up high so the water that comes off the trailing edge curls upwards due to the stern being lower. You want the transducer to "skim" off the water surface. In fact, some diagrams prefer you to angle the transducer up instead of down to account for the angle of the water flowing through the transducer when planing. Always remember you are trying to make the transducer parallel to the flow of the water and not necessarily the water line on the boat when its sitting still.

    It will take multiple adjustments to get it just right. If you make any adjustments, try to only one change at a time. Don't raise or lower it and change angle. If it gets better or worse, you don't know what caused it to get better or worse. Find where you think it should be and then make one adjustment at a time, such raising the height or changing the angle. Its like going to an eye doctor. They make one adjustment and ask you if its getting worse or better and then make another adjustment. You need that feedback to know if what you changed makes it better or worse.

    The vertical angle is the easiest. Go on a plane, and turn left or right slowly. If you get better signal on one side vs the other side, that means you need to tilt it towards the side you are turning by a few degrees. Make sure you mark your spot with a pencil so you can repeat it if you have to loosen up the screws. Once you find a good vertical angle, mark a line parallel to your transducer so you know to keep that angle if you have to move it up and down.

    After that, I would adjust the up/down height and then the angle. If you do one thing at a time and spend half a day doing this, you can dial it in one day. Once you are happy, mark the spot and don't touch it. Take some photos for reference in case you need to adjust again later for different reasons.

    1625435396665.png
     
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    plj46

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    Jan 7, 2008
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    Am i wrong here ? that transducer looks like it's mounted backwards ? the pointy end is to the rear.The blunt end forward.I see it fits the bracket but is that the right bracket for it ? It does look too low.
     
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    plj46

    I Post A Lot But I Can't Edit This
    Jan 7, 2008
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    That bracket looks identical to my Lowrance bracket.
     
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    ShadowX

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    Oct 10, 2010
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    Sure look backwards to me to and if its a garmin then yes it is

    Good catch! The rounded lip is to help break up the water in the front side. It may still work the other way around at slower speeds, but once you get on plane, that turbulence would make it hard to read bottom at higher speeds.
     
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