Depth Finder Issue

Each time I turn my trolling motor on, I loose most of the picture on my finder. The depth reading is still present and correct, and the finder continues to show the bottom detail. However, everything between the surface and the bottom (fish, structure, etc.) disappears.

It does not have to do with the speed. I do not have this problem when running the outboard, or being pushed by the wind/current. Also, the transducer cable and the trolling motor power cable are not run parallel, so that is not the issue.

Could it be that the trolling motor and finder are tied to the same battery? Any other ideas? I would appreciate any thoughts you may have.

my fish finder was on the same battery as my trolling motor. I bought a cheap 12v lawn tractor battery to run the fish finder and the problem was solved. The lawn tractor battery will power my Lowrance LMS336iGPS all day without a problem. It's not a deep cycle battery, so I recharge it after each use and it will last 2-3 years. (not bad for a $20 investment).

Your finder should be on your cranking battery! If it's not move it to the cranking battery.

Your trolling motor should be the accessory on your deep cycle battery!

I had a problem like that. When ever I ran my trolling motor it would wack out my sounder, I ran a groung wire from my trolling motor mount to the negative side of the batteries and made the problem go away.

The only thing that should be on the trolling motor battery is the trolling motor. When you step on the tm's go button the initial current draw is high. This causes the voltage to go down. Sensitive electronics in your depth finders do not like that fluxuation in voltage and it can damage them.

I have been running my front mounted fish finders off of the trolling motor battery for 26 years now and never had a problem......also running the front electric anchor off of it. Had it like this for 22 years on my old BassTracker and going on 4 years now with my G3.

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Originally Posted by G-3 Fisherman

I have been running my front mounted fish finders off of the trolling motor battery for 26 years now and never had a problem......also running the front electric anchor off of it. Had it like this for 22 years on my old BassTracker and going on 4 years now with my G3.

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Ground isolation, trolling motor voltage, connector quality, wire size, quality of fish finder, etc. can all effect how much of a problem you will have or won't have. ISBN is right according to the fish finder makers. Doesn't mean what you've been doing ain't right, cause it's been working out great for you. But that doesn't change the problem the OP is having.

I think the OP should look at isolating his fish finder from his trolling motor battery. DC motors are really good electrical "noise" makers.

I run just the TM off one battery... everything else off the starter battery

Its a possibility that the OP's problem is due to some poor wireing connections. I do not care for twisted and taped connections and I certainly do not like the crimp on butt connectors etc. All the connections on my boat are good mechanical connections ( clean and twisted tightly), soldered properly, and then sealed with heat shrink tubing. I would be interested to know....if the OP's problem has been there all along or just recently started.

Simple solution is to move the FF to the cranking batt. Some, like G-3 don't have problems, but the safest bet is to move it. Not everyone can be "Special" like G-3.

Wannabe...

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Originally Posted by Wannabe...

Simple solution is to move the FF to the cranking batt. Some, like G-3 don't have problems, but the safest bet is to move it. Not everyone can be "Special" like G-3.

Wannabe...

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Never said I was special Chris.....just stated what is working for me. I am interested in finding out more about this however.

Speck-Tackler,
What brand and model depth finder do you have?
These are good starting points: check and see whether it is powered off of the cranking battery or not and ensure that all of the electrical connections are tight and not corroded.
Does the problem go away when running at the highest speed?

There are two things that I love about this site...

1. there are a LOT of folks here that are a LOT smarter than me :D, and

2. Everyone I have encountered on this site goes out of their way to be helpful!!!

That said, I am going to move the depth finder connection to the cranking battery and see if that solves the problem. If not, I will be back, seeking other ideas.

I do have one question about running the finder off the cranking battery... the finder circuit is fuse protected, but is there any concern (surge) related to cranking the motor when the finder is connected and powered on? Would I need to power the finder off and/or disconnect it before cranking the outboard?

Thanks again.

This should not be a problem as long as you have a large enough amperage battery. This becomes a problem when the battery capacity is too small, the battery has lost some of its capacity (due to age or neglect) or connections become dirty, loose or corroded.

I have a tricked out Jon boat and run everything off one battery, haven't had a problem similar to this, everything is TM, DF, aerator, and lights. ONly problems I've had with the DF have been due to corrosion in the line connections and the fuse holder.

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Originally Posted by G-3 Fisherman

Never said I was special Chris.....just stated what is working for me. I am interested in finding out more about this however.

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Akshually G-3, I've always considered you speshul, not special. :)

If the move to the cranking batt doesn't solve your problem, you've got some other gremlin. The easiest full solution is to strip all electrical wire and replace it taking extra precaution about connections and what is next to and adjacent the wire run. However, G-3's tip of running a ground wire from the TM foot to the negative side of your batt will most likely solve the problem as well.

While you're at this, it'd be a good time to check the age and water level in your batts, clean all connections and apply dielectric grease to the terminals.

Wannabe...