Electrical interference on trolling motor

griz01 · Post by **griz01** » Sun Dec 28, 2008 8:24 am

Everytime I step on the power for the trolling motor I get lines & dots across my screen. When I take it off they go away. I've had this set up since I bought it new and it's been doing this for a couple of months and I can't figure out what to do. I have seen that when I take the transducer off the motor and push the power button it doesn't do it. Is there a way to fix this without having to possibly buy a new transducer? Or could it be something else? I have a Lowrance X125 and Minnkota trolling motor. Anybody help

MIKE TREMONT · Post by **MIKE TREMONT** » Sun Dec 28, 2008 8:33 am

Check you transducer cable. I've gotten a small slice in the past and had similar problems.

I have a continuing problem like you described with no fix. I've tried many remedies with no help.

I hope you have better luck than me.

minnkotaman · Post by **minnkotaman** » Sun Dec 28, 2008 9:16 am

this came up 20 years ago when minnkota first came out with the maximizer circuit, it forced the guys making sonar curcuits to put in a filter in their curcuits.
no 1 the locator and the electric should be on seperate batteries,
the feed back comes thru the negative side of the battery.
the only other fix is to make a ground wire and put it on the negative side of the battery that drives the electric and put it to a good ground on the boat, (the mounting bolts are best).
that should take care of any interference.

bassman619 · Post by **bassman619** » Sun Dec 28, 2008 9:47 am

here is some info that I found, hope it helps. BTW I've tried everything and still have some interference with the TM.

http://mysite.verizon.net/restmvit/tmintf.html

Joe Bruce · Post by **Joe Bruce** » Sun Dec 28, 2008 9:59 am

Iv gone so far as to have a battery sitting on the deck for only the graph, the transducer mounted on the end of and old broken off rod that I could throw out and move away from. the graph was mounted on a piece of wood.

so nothing with the graph was connected to the boat.

still interference, until I went into boats with a 5 speed t motor speed control.

so I bought a 5 speed , no more interference

ken L. · Post by **ken L.** » Sun Dec 28, 2008 10:03 am

I had the same problem with my trolling motor. What I did was go to a 12 volt motor cycle battery and wired it direct to sonor unit, and no more lines when I hit the trolling motor switch. Motor cycle batteries are about 1/5 the size of a regular battery. I have been usiing the this system for over 5 years and still going strong. The only thing is that you have to remember to keep the charge up on it.

scottkh · Post by **scottkh** » Sun Dec 28, 2008 10:33 am

If the fish finder is a Humminbird unit, call Humminbird Customer Resource folks at 1-800-633-1468 and ask for trolling motor interference kit.

JLS (Jay Liu's Service) · Sun Dec 28, 2008 11:02 am

Make sure that your transducer cable is not routed down with the steer cables. next go to menu (on the graph) adjust the noise rejection to high, then adjust the sensitivity to 75 or 80 percent. This should take care of your problem. If this does not work, call me #530-246-8051 I can ask more question and may correct the problem.

Jay (JLS Jay Liu's Service, Trolling motor repair)

minnkotaman · Post by **minnkotaman** » Sun Dec 28, 2008 11:03 am

this is from he minnkota service manual.
Chapter 2.
Depth Finder Interference
Variable speed motors with a PWM speed control / Maximizer circuit can sometimes
interfere with the operation of a depth finder. This can be due to RF (radio
Frequency) or electrical interference.
NOTE: this procedure is for pre-Universal Sonar 2 units only.
For more information regarding Universal Sonar, see Chapter 3.
Here are a few steps to reduce or eliminate the interference problem:
If the motor interferes with the depth finder when both are being operated:
Step 1. Determine if supply voltage for trolling motor and depth finder is provided by the same / common battery.
A. If yes, disconnect depth finder battery leads from the trolling motor battery and connect them to the
engine cranking battery.
B. Test depth finder for interference while operating motor.
NOTE: Steps 2-5 DO NOT apply to Universal Sonar 2 units!
Step 2. If interference is still present at Step 1B, proceed as follows:
A. Connect a light gauge wire (18 gauge is fine) from the negative post of the trolling motor battery to the
negative post of the engineâ€™s cranking battery. We suggest installing a 1 or 2 amp inline fuse in this
ground wire. (Minn Kota P/N 2060310 is the fused grounding wire.)
B. Test for depth finder interference while operating the motor.
Step 3. If interference is still present after installing the ground wire, proceed as follows:
A. Check the routing of the depth finder and trolling motor battery leads. If they run parallel to each other
for any length of distance, separate the leads as much as possible or run the leads to the trolling motor
and depth finder on opposite sides of the boat.
B. Test depth finder for interference while operating the motor.
Step 4. The brush shunt wire may be inadvertently touching the inside of the motor case. This is more apt to happen on
4â€

mm · Post by mm » Sun Dec 28, 2008 12:45 pm

Try running a wire to externally ground the motor.
Drill a small hole in the skeg on your TM, connect the wire to the skeg and run it up the TM shaft with the transducer cable.
Connect the wire to the ground wire that goes to the light for the directional arrow inside the TM head. Make sure to cover the splice with tape or heat shrink material.
This has totally eliminated any interference for me.
Lowrance X135 Minn Kota 101
I have tried many other remedies that didn`t work well, this is the most simple and worked for me.
Good Luck

griz01 · Post by **griz01** » Sun Dec 28, 2008 7:02 pm

thanks for all the input, I guess I have some work to do. I even got a suggestion to put a small thin piece of rubber between the transducer and the TM. guess we'll see.