# Trolling motor/sonar interference "quick fix"



## Louie B (Feb 20, 2012)

I know a ton of people deal with this issue.  I've owned 3 boats the past ten years and two had this issue, I've had no telling how many clients ask me about this.  

So with that in mind, we decided it would make a great article for BGS.  Adam Broughton former aerospace engineer and product mgr w/ Humminbird took the time to address everything you need to know about interference on your boat including the pesty trolling motor/sonar interference issue.

The article is broken in sub-titles so, if you're interested in the trolling motor interference fix then look for the title "The #1 fix"  The entire article is an interesting read, enjoy and we hope this helps.  Here's the link.

http://www.biggeorgiaspots.com/boat...r-stuff/180-aaargh-sonar-noise.html?showall=1

LB


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## creteus (Feb 20, 2012)

Good read indeed


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## Terribleted (Feb 20, 2012)

I have been trying to eliminate interference from my outboard or tach signal on my Hummingbird 998 mounted on my console. Interference varys with outboard rpm and is gone when the outboard is below about 1000 rpm.  Any ideas?   One idea that I have is that the tach itself is next to the finder I can move it 3 inches away by swapping it with the speedo..( I will try this this week). The other Possible issue is that the transducer wire is routed along side the wiring harness from the motor to the console (if this is the source it is a bit harder to eliminate by moving stuff as there is no good way to route the wiring elsewhere without taking most of the interior riveted panels, floor etc. out of the boat, or running the transducer wire on the surface of the rear casting deck floor etc....) Perhaps a ferrite magnet as suggested in the article.  Any other  ideas would be appreciated.


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## Robert Eidson (Feb 20, 2012)

Very good read LB !!!!!


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## ABroughton (Feb 20, 2012)

Terribleted, is your trolling motor and sonar on separate batteries (kidding, kidding....)

Seriously, try running a direct line from the cranking battery to the sonar, rather than to the bus --(bus is the breakout panel under your dash). You're probably getting noise from the distributor cables, but its hard to say where its entering the system. 

I would bet the transducer cable being bundled with the motor cables is the culprit. Are you certain there is no other way to route it?

-Adam


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## T.P. (Feb 20, 2012)

I had issues with a 597. When I would use the TM the sonar would completely yellow out and was useless. I have only one route from the console of the boat to the transom so I had no choice as to wire routing. But... I did in a futile attemp try to just lay the wires on the floor as far away from any other wire and hooked to a seperate battery. Still no go. I even called humminbird and they told me to try what I had already tried and finally the sent me a choke that didn't work either. It was either remove my MinnKota Terrova or my Humminbird. I still have my Terrova.



http://forum.gon.com/showthread.php?t=621226&highlight=humminbird


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## Terribleted (Feb 20, 2012)

ABroughton said:


> Terribleted, is your trolling motor and sonar on separate batteries (kidding, kidding....)
> 
> Seriously, try running a direct line from the cranking battery to the sonar, rather than to the bus --(bus is the breakout panel under your dash). You're probably getting noise from the distributor cables, but its hard to say where its entering the system.
> 
> ...



 I am betting that the xducer cable paralleling the motor harness is the problem as well.  Routing it any other way beside on top of the floor etc. would be very involved. I had thought about your suggestion of running a direct power feed (lol my idea was to run it from the trolling motor battery....hmmm..that would likely cause a different problem from what I just read...right now I have zero interference when running on the I-Pilot). I will take a long enough piece of lamp cord next time I go out and try direct wiring to the start battery...easy to do...might help.  Maybe I will wrap the entire xducer cable in foil grounded foil and see if that helps


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## ABroughton (Feb 20, 2012)

The ferrite ring is probably a good option for you too, T'b. That would be a really easy fix worth trying if you can get your hands on a ring magnet.

I have seen people dismantle a busted speaker to get a big ring magnet. Junkyards are full of them, you know?

FYI--the transducer cable is already shielded/grounded internally. If you cut the outer sheath a little you'll see the silver foil in there. (hypothetically speaking---don't cut your 'ducer wire)

Your power cables aren't shielded, but normally, any noise picked up in the power cables can be filtered out in the unit---but not always, which is why the more sensitive units ship with a ferrite ring built into the power cable. ($ferrite ring < $shielded cable)


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## Terribleted (Feb 20, 2012)

I think the 998 Hummingbird has such a device in the power cable. I believe that is what the round plastic covered fat thing near the end where it plugs into the back of the unit is.I knew that the xducer cable is already shielded, but I still need more noise abatement.  Ferrite ring around the gps and xducer cable is also a good idea.  Speaker magnet...super idea....hmmm I may have an old speaker lying around...will have to rummage in the basement


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