Interference on Humminbird Sonar

I have a Humminbird 777c2 mounted on the bow of my boat, the sonar transducer is mounted externally on a MinnKota TM. How do I identify the interference/noise that I see on the sonar?

not sure I understand, by identify do you mean determine where it's
coming from? By any chance is it vertical blue bars that show up mostly
on the bottom half of the screen, mostly when the tm is on say, 1/2
or more? Reason I ask that is I'm running a similar set up, and that's
what I have. Haven't had time to try and fix mine yet.

I have found out my problem shows up with the 83 wide beam,
if I turn it off or cut the sensitivity down to nothing it goes away.

Is it there all the time? Or just when the TM is running? Which battery are you getting power for it from? TM or starting?

There is a ground wire kit Minn Kota has that you can go to your nearest service center and have it installed on your trolling motor. If you dont have one near you, give me a call at 1-800-305-9866 and I can take care of it!

I had it on mine till I moved the power off the trolling battery to the cranking battery. fixed it right up.

J White, yes I mean where the interference is coming from, you are exactly correct with the blue vertical lines which extend from the bottom to the top of the screen or sometimes from midlevel to the top. It only occurs when the TM is at 30% or greater. I have also reduced the sensitivity on the 83 and the interference is reduced but I do not get the picture definition I need.

IBNFSHN, Interference is only there when I run the TM, power source is from the cranking battery.

There used to be a FAQ on Minnkota's web site that addressed that problem. They had you put a piece of rubber between the xducer and the motor and install a ferrite coil on the pos lead going to the depthfinder. I'm not familiar with it but I suspect that the ground wire that Osofishy mentioned may be a better fix. At least it makes sense to me. You would think that they would have that on their web site.

Good info guys. Would've posted back sooner, but didn't want to just jump in and muddle up the thread before the original poster's questions got answered :)

I'm running a 787 on the US2 transducer. I thought the ground wire would've
been somewhere in the box with my Terrova when it came in, but didn't see
anything like that. I'm running off the cranking battery too, but MAY have
some wires routed closer together than they should be - just ain't had time
to really dig into it. Osofishy, thanks, if I get around to trying a fix, I may
be hollering at ya.

Have ya'll with US setups noticed that they seem REAL sensitive?
I had a Vexilar flasher on a Maxxum/US1 before, and both it and the
setup I have now seemed like I needed only the lowest possible settings on
sensitivity - For example, I'm running the main setting on like "2" out of a
possible 20, and it is giving way mucho detail - even in deep water. Not
that that's a bad thing, just surprised me.

Try taking a black wire and connecting it to your negative terminal of your trolling motor battery.Then take a ground it directly to your boat(on an aluminum one of course)I usually do it right in the battery storage compartment.Alot of times this will take care of the interference problems.As someone else said about a piece of rubber to isolete interference from the armature, but Ive only heard of that on some of the older Motorguides.PJ

that ground wire - on a 24V system, hook it to the negative post that my
negative side of the tm leads are hooked to, not the other one which
is jumpered to the + of the other battery??? I am confusing me even :D