Trolling Motor & Graph Interference

[fozzype]

Having issue with the dreaded spike between my trolling motor and new graph.  I have the new echomap garmin and a nearly new digital 109 motorguide.

The transducer is mounted on the trolling motor.  I get a spike as show below when on variable speed.  It is less on high bypass.

This not isolated to garmin and I have been pleased other wise. 

Any ideas on how to  fix this or at least make it better?? 

Scott at Marine Repair  said it is strictly a trolling motor  issue.  Also, there is a wealth of  information on the old Internet about this but nothing substantial.

Just thought this group might be seeing same thing or have sorted this out before.

 

[Ketchup]

Read this.  Especially #5 and then the last paragraph of the page. Try that to start. 

 

http://www.vexilar.com/blog/2014/08/28/solving-sonar-interference

[176champion]

Try this also .......http://www.bbcboards.net/showthread.php?t=687886

[Bass Enforcer]

Fozzy, I am sorry if you learned this fix already as I did not read the other details on the comments because I just had the same experience. I have since learned how to fix mine and it is extremely easy. All you need to do is ground your trolling motor. Remove your wire harness from the bow of your boat. You will see the black wire/screw. Once you have located it, take a piece of 16 gauge wire and strip both ends. Touch it to the screw with the black wire (ground screw) touch the other end to your trolling motor head.  This should clear it up. If it did not touch, it to the other black screw.  Once you are convinced you have the problem resolved you simply have to route your wire down the trolling motor shaft and attach it with a hose clamp. Hope this helps. If it doesn't just private message me. I'l give you a call and walk you through it.

[fozzype]

Thanks for all your help on this..

 

I have a very simple solution that  has cured all interference on all that have tried it.

You need a price  of high voltage protection  mat  like linemen use to prevent transfer of energy from the ground to them should it be energized.  It is a soft rubber mat with laced copper threading about 1/8 inch thick.

A link is below to show you the product.  It is pricy so you will need to do like I did ... I got a scrap piece from a buddy of mine who is an electrician. Some of these don't test and are not allowed for use anymore.  Most electricians or linemen will have some or can get you a peice.

https://m.grainger.com/mobile/category/shock-protection-blankets/arc-flash-protection/safety/ecatalog/N-cfx

You take a price and put between your transducer  and motor and between the motor and hose clamp that hold the transducer on.

I had zero interference  after doing this and did nothing else.