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Fishfinder interference


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Hey guys,

Recently installed a Garmin Striker 7 SV and it's transducer and am getting some horrible interference. I was wondering if you guys could help me troubleshoot it. The first pic is sidescan and shows a heap of lines/noise appearing at only 3.3km/hr. The second shows traditional and downscan and the same thing but with some missing data this time at only 2km/hr. The 3rd and 4th pics show a wreck and some pylons that I went past to test sidescan, as you can see its pretty hard to make out anything.

As you can see it is quite debilitating and pretty much renders the fishfinder useless. I have tried several things to fix it already, none of which have seemed to help. I have all my electrical accessories including the sounder running through a switch panel, and the negatives are connected to a bus bar which runs back to the battery. I do not have a trolling motor or marine radio installed. The outboard motor is currently not connected to the battery as I have not got around to connecting it yet.

It should also be noted that these problems occur at anchor aswell, so I'm pretty sure its not a problem with turbulent water or transducer placement. I also tried it at anchor with all other electronic devices off and the motor (which was also off) is not connected to the battery, so does that rule out electrical interference? Or could there still be interference from the switch panel or other electrical wires?




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Hi Biggest Kid

I don`t know if this will help you or not, as I don`t know  to much about  garmin finders as I have a lowerance  but with your side scan I see you have chirp 800 KHZ selected have you tried changing it down to say 455KHZ or lower if possible, as well as changing how far out to each side it covers and your contrast.

I find with my lowerance that I get better soundings on side scan if I turn my contrast up and lower my KHZ.


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As aboveI have no probs with the lowrance. I also find using the lower frequency of 455 better even in shallow water where the 800 should be best. Those lines look how mine is while travelling at 40kmh but as you say you are travelling slow, even drifting, however the last image shows its managed to sort its self out and produce a decent image.

I have my sidescan transducer directly attached under the centre of the hull just ahead of the engine. Before that the transducer picked up on the engine if it was trimmed in.

The traditional down scan in blue looks week as if more sensitivity is needed (or transducer placement is wrong), its loosing bottom at low speed in shallow water.

I know you think you have the transducer set well but my money is going to be on where its placed or maybe the angle. Im sure with a little tweaking you will soon have it sorted. As mentioend do you have an image of the back of the boat.

By the way I first thought you had a temp problem but noticed you are from Cairns. 

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Yeah I do have some pictures of my old transducer placement. I have since moved it down so that the halfway line of the transducer is level with the bottom of the hull. I have also tilted it down at the back ever so slightly. I do however stress that those first 2 photos were taken AT REST, so transducer placement cannot be an issue.

And raging what do you mean by borrow a 12v battery and power straight off that? It is already powered from a 12v battery?

Also yes I could lower the frequency to 455, but that would also lower target resolution which I'm not too keen on. Doesn't that defeat the purpose of having access to 800khz in the first place? It should be able to work at 800khz if it was designed to, I should not have to settle for second best.



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