T.M interference the moment the T.M touches the water- ground case from inside ?

Recently added a Lowrance StructureScan. Love it but whenever I turned on my trolling motor, a Motorguide W75 wireless (pulse modulated of course), screen went almost all white and could not see a thing. Trolling motor wiring is on opposite side of boat, LSS-1 is on cranking battery, wires share nothing - transducer is mounted on the transom. Tried various things and nothing worked. So went to the lake yesterday and took a small lawn tractor battery and wired it directly to that, right beside the LSS-1. T.M was up, and i tested it by turning on the motor real quick - great, works fine so my problem is in the power wires.
thinking it "fixed" for the moment, headed out to do some fishing. dropped the T.M in the water, turned it on and the screen goes white....
playing around with it, I figured out that it happens the instant the trolling motor hits the water.
It is NOT the wake from the motor - the wake would not even have time to get back to the transducer (also works just fine with the main engine up to over 20 mph). Is just the moment it touches water.
I am going to guess that I just need to add a ground to the motor casing itself ?
The "bummer" of this is the way the Motorguide W75 mount is - is really hard to run wires up the shaft - people have a hard time figuring out how to run the cable if they mount a transducer on it.
So, was wondering.......
there are 2 wires going to the motor - if I did determine that running a ground to the case fixed my problem, could I possibly run the ground to the ground wire INSIDE the motor itself ? Attaching a wire to the case then splicing it into the ground wire running to the battery ?
Obviously the problem would be attaching the wire inside the case, but I am thinking that will be easier to figure out than figuring out how to run the wire up the shaft - at least a whole lot prettier. I can see where I would have to drill a hole in the case (voiding my warranty), but i am sure I could fill the hole so it never leaks.
Anyway - 1st is that probably my problem - I won't be able to work on it again until tomorrow. And 2nd - can i run the ground to the actual ground wire to the motor itself.
Thanks for any info

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Originally Posted by donberry

Recently added a Lowrance StructureScan. Love it but whenever I turned on my trolling motor, a Motorguide W75 wireless (pulse modulated of course), screen went almost all white and could not see a thing. Trolling motor wiring is on opposite side of boat, LSS-1 is on cranking battery, wires share nothing - transducer is mounted on the transom. Tried various things and nothing worked. So went to the lake yesterday and took a small lawn tractor battery and wired it directly to that, right beside the LSS-1. T.M was up, and i tested it by turning on the motor real quick - great, works fine so my problem is in the power wires.
thinking it "fixed" for the moment, headed out to do some fishing. dropped the T.M in the water, turned it on and the screen goes white....
playing around with it, I figured out that it happens the instant the trolling motor hits the water.
It is NOT the wake from the motor - the wake would not even have time to get back to the transducer (also works just fine with the main engine up to over 20 mph). Is just the moment it touches water.
I am going to guess that I just need to add a ground to the motor casing itself ?
The "bummer" of this is the way the Motorguide W75 mount is - is really hard to run wires up the shaft - people have a hard time figuring out how to run the cable if they mount a transducer on it.
So, was wondering.......
there are 2 wires going to the motor - if I did determine that running a ground to the case fixed my problem, could I possibly run the ground to the ground wire INSIDE the motor itself ? Attaching a wire to the case then splicing it into the ground wire running to the battery ?
Obviously the problem would be attaching the wire inside the case, but I am thinking that will be easier to figure out than figuring out how to run the wire up the shaft - at least a whole lot prettier. I can see where I would have to drill a hole in the case (voiding my warranty), but i am sure I could fill the hole so it never leaks.
Anyway - 1st is that probably my problem - I won't be able to work on it again until tomorrow. And 2nd - can i run the ground to the actual ground wire to the motor itself.
Thanks for any info

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nonononononononono I think that is an interrupted ground that works with the PCM...Cane Pole will probably see this and give you the correct answer...

Like DonG stated, Be careful of where you ground your housing. Motorguide ustea have the pwm circuit internal (in the motor housing), but I believe they now have a pwm arrangement similar to MK. I would suggest staying away from the internals of the motor. Sometimes we just have to work for our pleasures. If you do run the wire, I would suggest following the guidelines posted in the sticky about TM noises. I believe it was 18 ga with a 3amp fuse. Ima just swagging as I don't know for sure. You be the judge.

okey dokey - appreciate the info. Guess after I see if it is the problem (hopefully as I am running out of ideas) I will figure out the wire issue. Bummer in a way - I just changed my column to a longer size - I could have run the wire thru the shaft, drilled a small hole to get it out, then use a rubber plug and sealed it good with silicone. Taking off the old shaft was a bear and doubt I could get the new one off without marring it up pretty good.

Quote:

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Originally Posted by donberry

okey dokey - appreciate the info. Guess after I see if it is the problem (hopefully as I am running out of ideas) I will figure out the wire issue. Bummer in a way - I just changed my column to a longer size - I could have run the wire thru the shaft, drilled a small hole to get it out, then use a rubber plug and sealed it good with silicone. Taking off the old shaft was a bear and doubt I could get the new one off without marring it up pretty good.

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We have all been thru it. Sux for sure.