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  1. #1
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    73SV major interference when moving slow

    echomap 73sv non-chirp

    Spent some time with a 73SV today that is mounted on an aluminum boat with pontoons that stick out a little past the transom (mounting photo coming soon)

    The unit gives great side view photos, but picks up a strong return at 2.5 feet down on the left side. The main issue is that when you slow down or drift with the wind, interference becomes worse and is repeated at consisted depth. I cannot figure out why running at a fast speed eliminates the issue

    This is a shot after the boat is picking up speed and the interference starts to clear up


    Image when drifting . The same interference is seen on the clearvu screen




    So is sonar hitting the pontoon and bouncing back to the unit causing some kind of repeat effect? Why does this happen when boat is moving slow and not when it's moving fast, and why doesn't the same issue happen over the the right hand side with the other pontoon?

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    #2
    We need to see how its mounted in relation to the engine and pontoons.

    Are you powering the boat with an electric trolling motor or the main?

    When drifting - is everything off - including the engine and/or trolling motor?
    Smokercraft Phantom 202 Yamaha F115/Merc 9.9
    Garmin 7610xsv/GT51M-TM/Panoptix PS21/LiveScope
    Why am I hanging out here when I could be fishing.....

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    #3
    Will get picture of how it's mounted ASAP. We forgot to take one when we got it out of the water

    We were using the main outboard

    No other electronics were on when drifting and we were the only boat on the water

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    #4
    And the main engine is also off when your drifting?

    This is quite the mystery. I am having trouble coming up with any reasonable ideas so far.

    Need to see the install pics.
    Smokercraft Phantom 202 Yamaha F115/Merc 9.9
    Garmin 7610xsv/GT51M-TM/Panoptix PS21/LiveScope
    Why am I hanging out here when I could be fishing.....

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    #5
    Thanks for help Larry. I have spent a lot of time with marine electronics and have not seen something like this. I am very confused by how it works when going at a very fast idle but slow idle has interference. At fast idle the interference is still there, but it's just at the 2.5ft depth and not a big deal.

    I was describing the extensions on boat as "pontoons" only because they is what they call them. It's really just and extension of the boat almost like a step. Original thought was that we may have to mount ducer on back of one of them, but we went with traditional mounting location first

    yes big motor is off when drifting with wind. The Garmin was only electrical device on

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    #6
    Very unusual for sure.

    If it was just a difference between slow idle and fast idle, I would suspect your charging system on the motor - faulty regulator or diode maybe - but since it gets worse when he engine is completely off, that throws things for a loop.

    I just had a thought.....

    What battery is powering the MFD?

    Do you have two batteries or three or? If so, do you have an ACR or other automatic switching device for charging/connecting the two/three/etc batteries together? Sometimes, they can go into a very fast switching mode.
    Smokercraft Phantom 202 Yamaha F115/Merc 9.9
    Garmin 7610xsv/GT51M-TM/Panoptix PS21/LiveScope
    Why am I hanging out here when I could be fishing.....

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    #7
    I will have to ask him. It's not my boat. Pretty sure just one trolling battery and one for starter. Here are some photos. Obviously not ideal setup, but the starboard side extension doesn't seem to be a factor. Not even certain the port side extension is causing issue but seems likely. Not sure why it seems to clear up when running fast either




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    #8
    I have learned that the extensions are called sponsons

    There was a very old humminbird transducer in same location previously and it didn't have any interference. The Garmin is even picking something up on 2d

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    #9
    The interference has to be the sound hitting the sponson and then echoing back which is why it's worse when it's sitting still. Maybe when boat is going faster it doesn't have as much time to echo back and forth and that is why interference gets weaker the deeper it goes. I was able to find some old posts with people having same situation but no real solution yet

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    #10
    Wow. It's hard to imagine a worse place to put a sideview transducer!

    I think your right - it pretty much has to be the sponsons reflecting the signal back and forth with some echos off the lower unit added in.

    Its still hard to see why the interference would get that much better when the boats moving. Perhaps the turbulence between the sponsons is blocking it to some degree. Im betting there would be a ton of turbulence. Thats the only thing I can think of.

    There is an easy test. Just unbolt the transducer and drop it down lower in the water when sitting still. If it goes away when the transducer gets below the spnosons, you found your problem. It mau need to be several inches down to eliminate it all. The side lobes will reflect up as wella s to the sides when they are close to something.
    Smokercraft Phantom 202 Yamaha F115/Merc 9.9
    Garmin 7610xsv/GT51M-TM/Panoptix PS21/LiveScope
    Why am I hanging out here when I could be fishing.....

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    #11
    Im curious - why the sponsons? Are they to help offset the weight of a way over sized engine?
    Smokercraft Phantom 202 Yamaha F115/Merc 9.9
    Garmin 7610xsv/GT51M-TM/Panoptix PS21/LiveScope
    Why am I hanging out here when I could be fishing.....

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    #12
    I'm not sure on the sponsons, it's not my boat. Just trying to help him get it going

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    #13
    I wish him good luck. Hopefully, the fix is as easy as moving the 'ducer.
    Smokercraft Phantom 202 Yamaha F115/Merc 9.9
    Garmin 7610xsv/GT51M-TM/Panoptix PS21/LiveScope
    Why am I hanging out here when I could be fishing.....

  14. #14
    Quote Originally Posted by Larry3215 View Post
    Im curious - why the sponsons? Are they to help offset the weight of a way over sized engine?
    You see them a lot with duck boats. They help the boat float level with heavy mud motors and surface drives. Don't see many on outboard boats though.

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    #15
    yes the sponsons were added when the boat had a large fan attached to it

    We spent a lot of time testing different transducer locations and really couldn't get one that worked like it should. This boat stays on a small private lake and the main benefit to the graph is going to be the quickdraw. The unorthodox mounting location still picks up the sponson on the left, but it seems to be about as good as it will get for this setup.



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    #16
    Thats a huge improvement!

    You might be seeing the lower unit now. Try trimming the motor DOWN some more and it might improve a little more.

    Normally, trimming up is the way to go, but you now have the transducer behind the motor instead of in front of it. You will be picking up the prop wash as well, which you may be stuck with. The turbulence and bubbles from the exhaust will be very difficult to get rid of if the main is running. It should be a lot better if you run on an electric motor.
    Smokercraft Phantom 202 Yamaha F115/Merc 9.9
    Garmin 7610xsv/GT51M-TM/Panoptix PS21/LiveScope
    Why am I hanging out here when I could be fishing.....