Garmin unit and tm interference

[JK9027]

I'm getting blue biggly on the 2d of my newly installed 106sv with the 54 mounted on the tm. One of the many recommended fixes is a bond wire between tm and starting battery negatives. I've got a tin boat and as it sits now the tm is isolated from the hull. The starting battery is common with the hull, I’m assuming thru the Mercury. I'm concerned about tying both batteries together with the hull. Is it safe, will it cause electrolysis? Is this recommended for aluminum boats? Anybody done it and alleviated noise issues? Thanks

[MTW]

the starter B- is tied to the motor's sacrificial anode, which should be zinc in most cases (could be aluminum in some boats, which is why its a bad idea to use an aluminum battery extender). might help, might not. a lot of big boats has the B- tied together at a common bus bar. whatever you do dont create another ground reference in the front of the boat.

might try a 1/2" puce of rubber mounted between the xducer and the tm motor barrel. sometimes that will fix it.

[CatFan]

What 2D transducer and trolling motor are you using?

[JK9027]

It's a 24v maxxum 70 lb thrust and the gt54 transducer.

[CatFan]

It's a 24v maxxum 70 lb thrust and the gt54 transducer.

Interference still there at 100% thrust?

[JK9027]

No wide open it's gone. I'm thinking it's something to do with the speed adjustments.

[CatFan]

No wide open it's gone. I'm thinking it's something to do with the speed adjustments.

Your are correct. It’s the PWM speed controll.

[Bill Reynolds]

I'm getting blue biggly on the 2d of my newly installed 106sv with the 54 mounted on the tm. One of the many recommended fixes is a bond wire between tm and starting battery negatives. I've got a tin boat and as it sits now the tm is isolated from the hull. The starting battery is common with the hull, I’m assuming thru the Mercury. I'm concerned about tying both batteries together with the hull. Is it safe, will it cause electrolysis? Is this recommended for aluminum boats? Anybody done it and alleviated noise issues? Thanks

Concerning the bonding wire:
Unless your MAXXUM is an old model, There should already be a bonding wire in the circuit. You can check this by removing the head cover and see if there is an inline fuse holder there. This fuse is on the wire that grounds the brush housing in the motor to the Tm Ground circuit. This is intended to take the electrical noise generated at the brushes and run it to ground. You should also check to be sure this fuse is not blown.
Several years ago, I tried connecting the ground of my 24 volt circuit to the motor circuit. It did not create electrolysis but it did not correct the electronic interference either. Over the years, I have seen several cases of electrolysis on both glass and aluminum boats and have yet to isolate a single cause. This is a subject that continues to perplex me.
Concerning RFI interference:
This results from the variable speed control in the foot pedal. This electromagnetic noise is transmitted by air and can be picked up by the transducer and/or the depth finder power cable and shows up on the screen. Back when we only had two 2D frequencies to work with (82/200) I had some methods to clear up the screen but once CHIRP came along, those were not successful. I am not sure you can do this on the 106 but if so try turning off CHIRP to see if it helps. That being said, even if it does help, you may want or need the better signal of CHIRP. Sorry I don’t have more to offer on this part of the subject. I do have an idea that promises to shield the transducer cable from the RFI but have to wait for warmer weather to try it.
Someone suggested putting a rubber pad between the motor and transducer and this is worth a try. I think there is a UTube video about this.

[JK9027]

Yeah, if I turn chirp off and gain down to 50% it's still a little blue tinge but I can see what the down vu shows....structure and fish identical on both. The fuse in the head is good. I think I'm going to lay a bond wire cross the deck from the unit battery to a grounding lug on the unit and tie my tm cables up away from the graph wires first. Probably look for some thick rubber padding too,

[Bill Reynolds]

Yeah, if I turn chirp off and gain down to 50% it's still a little blue tinge but I can see what the down vu shows....structure and fish identical on both. The fuse in the head is good. I think I'm going to lay a bond wire cross the deck from the unit battery to a grounding lug on the unit and tie my tm cables up away from the graph wires first. Probably look for some thick rubber padding too,

Assuming the noise is entering through the transducer cable these best practices may help:
1) Don’t run the transducer cable down the steering cable (i.e. get it away from the antenna). This is easy on the Fortrex or Ultrex bracket but I don’t remember how I did it on my MAXXUM bracket.
2) If your foot pedal is in a tray and the excess transducer cable is under the deck, it is buried in the noisy environment created at the foot pedal. I have heard of making a figure 8 bundle of the excess cable with a wire tie in the middle. This is a hack on the twisted pair concept used in Ethernet cables. I am skeptical of this one.
3) Ferrite Beads —- I would try the large bore snap together type so you can make multiple wraps around the magnetic core. this seems to be more useful on the power cable.
4) Electric chokes —- Minn Kota makes a choke that goes between the power wires from the battery and the foot pedal (as close to the pedal as practical), it definitely helped mine. It is part number TM-1.
There are no absolutes here but this may give you an orderly approach.

[Bill Reynolds]

I attached a Minn Kota service manual that discusses interference in Chapter two. Note this is an old document, pre CHIRP.

[JK9027]

Thanks alot. My cables are separate on the tm and I'm using the beads supplied but these are from garmin and only big enough for one wire pass, I remember multiple passes with hb. I'm pulling battery charger fuses too on next pass. If that doesn't clear it I'm going to run a sj 10 awg cord acrosseparated. To the unit and put all wires on the deck, separated. I'm going to try garmin and see what they think about the tm filter. Sounds like a good thing.

[lpugh]

Concerning the bonding wire:
Unless your MAXXUM is an old model, There should already be a bonding wire in the circuit. You can check this by removing the head cover and see if there is an inline fuse holder there. This fuse is on the wire that grounds the brush housing in the motor to the Tm Ground circuit. This is intended to take the electrical noise generated at the brushes and run it to ground. You should also check to be sure this fuse is not blown.
Several years ago, I tried connecting the ground of my 24 volt circuit to the motor circuit. It did not create electrolysis but it did not correct the electronic interference either. Over the years, I have seen several cases of electrolysis on both glass and aluminum boats and have yet to isolate a single cause. This is a subject that continues to perplex me.
Concerning RFI interference:
This results from the variable speed control in the foot pedal. This electromagnetic noise is transmitted by air and can be picked up by the transducer and/or the depth finder power cable and shows up on the screen. Back when we only had two 2D frequencies to work with (82/200) I had some methods to clear up the screen but once CHIRP came along, those were not successful. I am not sure you can do this on the 106 but if so try turning off CHIRP to see if it helps. That being said, even if it does help, you may want or need the better signal of CHIRP. Sorry I don’t have more to offer on this part of the subject. I do have an idea that promises to shield the transducer cable from the RFI but have to wait for warmer weather to try it.
Someone suggested putting a rubber pad between the motor and transducer and this is worth a try. I think there is a UTube video about this.

Bonding, drain wire, case ground, whichever the term used does not matter. to be more effective it cannot be on a current carrying circuit, it must be its own isolated circuit to the battery to work properly.
Most people get this wrong as they do not understand why they need two ground circuits, that fused bonding needs to on a separate path to the battery keeping the fuse

[Bill Reynolds]

Bonding, drain wire, case ground, whichever the term used does not matter. to be more effective it cannot be on a current carrying circuit, it must be its own isolated circuit to the battery to work properly.
Most people get this wrong as they do not understand why they need two ground circuits, that fused bonding needs to on a separate path to the battery keeping the fuse

I sort of understand, I have experience with shield drains in electronic circuits but there is no equipment/earth ground here. So I don’t know how to accomplish attaching the bonding wire to a non current carrying circuit. Does the ground/bond wire in the MK head accomplish that? Does the bond wire have to go back to the battery? If so which battery?

[JK9027]

IMO the bond wire goes straight to the negative side of the graph supply battery. Mine will anyway. I'm not sure why they call the return wire a ground. IMO a ground is attached to earth ground on one end. The return wire is part of a circuit and doesn't care if it's attached to ground. At one time ungrounded curcuits were common in manufacturing. Panels had ground lights on the front to alert that one leg had become grounded.

[Bill Reynolds]

IMO the bond wire goes straight to the negative side of the graph supply battery. Mine will anyway. I'm not sure why they call the return wire a ground. IMO a ground is attached to earth ground on one end. The return wire is part of a circuit and doesn't care if it's attached to ground. At one time ungrounded curcuits were common in manufacturing. Panels had ground lights on the front to alert that one leg had become grounded.

Thanks that’s what I needed to know.
I have been using the terms ground and bond wire very loosely and either creating or advancing the confusion. I too have a background in Plant Engineering and understand and agree with your reference to ground wires or lack There of.
It is just too convenient to say “the black wire is the ground wire” realizing that everyone knows what you mean.

[EdCas]

I get tm interference on all graphs. Disconnecting the starting battery from the onboard charger clears it up for me.