Electronic Interference

[Striper15]

I want to install a GPS/fish finder unit in the console of my jon boat and a fish finder up in the bow, with the transducer mounted externally on the trolling motor.  I called Eagle/Lowrance today, and they said I would need two batteries to do so. They said the trolling motor always needs to be hooked up to its own dedicated battery. Any and all electronics are to be powered from the boat's main battery. They said that if everything is running off of the same battery, that there would be way too much interference on the GPS/fish finder. They also said that you could only run one unit at a time for the same interference problems.

Not to doubt Eagle/Lowrance, but is this right? To be honest, I never really gave it any thought.

If it is true, what size and type of battery do I need to run the TM only?

Thanks for the help!

Eric

[scbassin]

1- You need a deep cycle battery for your T/M, either a size 27 or 31. If you have a walmart in your area they carry them.  Hook your T/M only to this battery.

2- I have a Minn Kota T/M & a Garmin 178c (GPS-Depthfinder) on the bow & a Garmin 250c & 2006c (depthfinder & chartplotter) on the console all are powered from the main battery & have no interference. The cone <'s are 14 & 20 degree's. If you fish deep water where the cone <'s could overlap you would have a problem. A 20 degree cone < in 10' of water would give you approx. a 3' dia. circle so if you have a 14' jon boat  you should be ok up to about 45'. If you have a Motor Guide T/M I understand that they can cause interference with the depthfinders mounted on them. I have also heard that sometimes due to harmonics that Lowrance will pick up interference. If that happens pick up a R/F filter from Radio Shack & install it as close as you can to the unit.

[ThomasL]

I have a jon boat with a lowrance x86ds depth finder and it is ran off

my agm group 24 battery that also runs my motor guide trolling motor

and the only thing i can see happen is when i hit the button to run the

trolling motor a can see the voltage drop from 13.1 to 12.9,12.8 but as

soon as i quit running it she goes back to 13.1 but thats normal.

One problem i have is when i get up in speed with the outboard

i'm experiencing cavitation turbulance around the transducer that

messes up the reading on my depthfinder,it'll read 15 ft then 88 ft!

I don't think thats a drop off a ledge,if so i need to stop and fish that!

[Raul]

If your transducer is mounted on the TM you eliminate the interference by coiling the transducer cable to the TM shaft, 2-3 turns around the shaft eliminate the interference when you power the TM and Finder with the same battery.

[fishbear]

ok if you do not mount the transducer to the TM but to the stern of your boat, is there any problem with interference using the same battery for both??  I am running my bow mount TM and my fish finder off the same battery, and every once in awhile my fishfinder goes a little bonkers,,, but I also know my transducer is bad, and Eagle is sending me a new one.  So maybe I need to just wait, and see if it still acts up with a new transducer;

[cart7t]

I'm not sure about feedback or interferance but the biggest problem with electronics on tm batteries is the on cycles of the TM.  When you hit the on button on the TM it can drop the battery voltage far enough below 12volts to cause all kinds of havoc with Fishfinders. Not damage mind you but the units could shut off or lock up and you'll have to cycle them on/off/on to get them back going again.

[Raul]

ok if you do not mount the transducer to the TM but to the stern of your boat, is there any problem with interference using the same battery for both?? I am running my bow mount TM and my fish finder off the same battery, and every once in awhile my fishfinder goes a little bonkers,,, but I also know my transducer is bad, and Eagle is sending me a new one. So maybe I need to just wait, and see if it still acts up with a new transducer;

In my personal experience I haven 't seen any interference. This year I mounted the transducer on the stern of the boat after having it mounted on the TM for over a couple of years, both are powered by the same battery, nope, no interference and both work at the same time all day long.

When I first mounted the transducer on the TM I did experience interference when I operated the TM ( snow, weird readings ), somewhere I read that if you coiled the cable to the TM shaft the interference would dissapear, I did that and no more problems.

The only problem of having the transucer mounted on the stern is that at speed you have cavitation and the finder can 't read.

[RollONTwo]

In my experience Cart hit the nail on the head. With the trolling motor off on off on along with the drain on the battery you might very well see things not natural with depth finders. They must have a certain amount of volts to function properly.

[Way2slow]

Lowrance does not sell batteries so they had nothing other than your satisfaction with their product to gain by telling you not to run your sonar off the TM battery.

Yes, many people with small boats that only runs one battery run their TM and Sonar off the same battery and don't see a problem.  Like the old thing, my grandpaw did it, my paw did it so there's nothing wrong with me doing it, just ain't quit right.

There are many problems that can be created by running your sonar off the same battery as the TM but since you don't believe the engineers that made the thing, I dang sure ain't gonna waste my time trying to explain them.

[Hale]

Soemthing that may help you overcome this...get a lawn mower battery from walmart (about 12 bucks) and run the finder of this. You will find that it runs forever and recahrging is minimal. Ive done this in the past on jon-boats and its worked really well for me.

Minimized headaches.