Texas Fishing Forum

987 interference

Posted By: Mike Keenan

987 interference - 11/07/16 02:16 AM

I was using my buddies boat today and he has two 987's on his boat. The one on the console works like a champ but the one on the bow gets all distorted when you activate the minn Kota trolling motor. It goes from reading normal depth to 250' then back to normal as soon as I let off the button and I know I didn't find a drop off...
any thoughts, concerns or what I should look at to figure this out? It's a pain in the butt
Posted By: 44 Diesel

Re: 987 interference - 11/07/16 02:50 AM

RF interference, the possible fixes are endless. First make sure the graphs are not wired to the trolling motor batteries. Make sure all transducer and power leads are not touching the trolling motor power leads. Has this been an issue for a while or just start. What model trolling motor are you using. What transducer are you using an external or a US2 inside the trolling motor? Some minn kota trolling motors have a fuse inside the head for this reason.
Posted By: Mike Keenan

Re: 987 interference - 11/07/16 01:54 PM

It's a Minn Kota maxxum and it's an older trolling motor too. As far as I know it's been going on for a while. This was the first time I took out the boat.
Posted By: UJC

Re: 987 interference - 11/07/16 05:01 PM

I found ferrite rings to be effective on HBs. I called HB years ago when I had a bird and they shipped it gratis. RF disappeared.
Posted By: Mike Keenan

Re: 987 interference - 11/07/16 05:58 PM

Where can I find these ferrite rings?
Posted By: Bobby Milam

Re: 987 interference - 11/07/16 06:00 PM

Humminbird sells them but they are proid of them. I will eventually just run to radioshack and grab a couple. They are pretty cheap there
Posted By: Mike Keenan

Re: 987 interference - 11/07/16 07:34 PM

You just clamp the rings on the power and transducer cables right?
Posted By: UJC

Re: 987 interference - 11/08/16 10:31 PM

I don't recall which cable I placed the HB ferrite ring on. But I went to Radio Shack and bought two more. I now have Lowrance at the bow. I place each ferrite on power, sonar and another cable I don't recall.

Visit this HB page . It should be useful for HB and other brands.
Posted By: Wayne P.

Re: 987 interference - 11/08/16 11:04 PM

Originally Posted By: Bobby Milam
Humminbird sells them but they are proid of them. I will eventually just run to radioshack and grab a couple. They are pretty cheap there


Humminbird has the TMC-1 that attaches to the trolling motor power cord.

Posted By: Bobby Milam

Re: 987 interference - 11/09/16 12:32 AM

Here is a video of the ring and how to use it.
https://www.youtube.com/watch?v=EM3xNctWaO4
Posted By: Mike Keenan

Re: 987 interference - 11/15/16 04:44 PM

Thanks guys, since my buddy is not inclined to do the work, I guess I get to work on it...
Posted By: Mike Keenan

Re: 987 interference - 11/23/16 02:28 AM

Will these ferrit rings go bad? There's one on his transducer cable now.. or maybe should he do the much needed update and hook the front fishfindee to the cranking battery?
Posted By: 44 Diesel

Re: 987 interference - 11/23/16 02:38 AM

They don't go bad. Do the proper wiring first then go from there. Keep all ff cables away from trolling motor power cables
Posted By: Mike Keenan

Re: 987 interference - 11/23/16 02:09 PM

As I figured, thanks
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