Fish Finder wiring.

Post your Jig, Spinners and spoon photos and directions here
Post Reply
User avatar
AJ's Dad
Commodore
Posts: 934
Joined: Fri Apr 03, 2009 6:34 am
Location: Millwood Wa.

Fish Finder wiring.

Post by AJ's Dad » Sat Jul 16, 2016 6:35 am

I'm still seeing what I believe is feedback from the alternator on my main motor, when I try to use my side finder imaging on my Humminbird 899 CI HD SI unit. It is cloudy in the center of the screen, and just not a clean image overall. When idling and watching the screen, I can lower my rpm's and it clears up some, making me think it is the feedback or interference I'm talking about. I have a 24V electric trolling motor, and I was wondering if I could tap one of those batteries for power to the Humminbird. I would think I can attach the wires to only one of the batteries and get the 12V power I need. My concern is, once the batteries are connected together to create the 24V system for the trolling motor. Would that connection create a 24V charge throughout that battery system, and send 24V to my Humminbird? I would hate to try it and burn up my fish finder. I know the trolling motor can tend to create the interference to but I only use the 899 when I'm at the steering wheel and looking for structure. Once I locate structure, I can use the side imaging on my finder located at the front of the boat.

Thanks in advance for the input.

User avatar
Larry3215
Admiral
Posts: 1858
Joined: Thu Aug 02, 2012 7:02 pm

Re: Fish Finder wiring.

Post by Larry3215 » Sat Jul 16, 2016 7:41 am

Mark, do you know how to do a screen capture on your unit? If so, a picture of what you mean by cloudy would help diagnose the problem.

Im asking because normally, electrical interference causes artifacts to appear all over the screen or in large patterns over the entire screen. You would expect to see rays or bars or splotches spread out over the entire screen and not just in the center. Something just showing up in the center of the sidescan image is much more likely to be a transducer placement issue.

Can you take a picture of the stern showing how/where the transducer is mounted? Get one pic down low so we can see along the bottom of the hull to see whats ahead of the transducer. Also one from the side might help.

Im guessing your problem is probably caused by something on the hull in front of the transducer causing turbulence or bubbles in the water - a step in the hull, a strake, water inlet or outlet, etc. It could also be reflections from the engine or a jackplate or another transducer etc.

This is all reinforced by the fact it clears up some when you slow down - less turbulence.

As far as tapping off one of your two trolling motor batteries, that would work if done correctly, but its a bad idea.

First I'll explain how to do the wiring, then tell you why not to do it.

With two batteries in series, one of them - battery A - has its neg lead connected to the black neg lead from the trolling motor. The other red lead from the trolling motor goes to the pos on battery B. Battery A has its pos connected to battery B's neg.

You must connect your sounder neg and pos to battery A neg and pos. Stay away from battery B. The reason is that you may have a common ground between your trolling motor batteries and the boat batteries and the sounder mount or something in the transducer. Connecting to battery B's positive and negative could create some serious issues like ground loops or even a short or galvanic corrosion issues. So only connect to battery A.

The main reason not to connect to only one battery in a series pair is that you will run battery A down lower than battery B - to some degree. Maybe a lot maybe not much at all. The risk comes in when you use your trolling motor a lot and run both batteries down low. There is a real chance of over discharging battery A and reducing its life or maybe even killing it completely. Your trolling motor only knows the total voltage Battery A + Battery B. It cant tell if A is lower than B, so it might let you run too long and kill A.

Hope that helps.

User avatar
AJ's Dad
Commodore
Posts: 934
Joined: Fri Apr 03, 2009 6:34 am
Location: Millwood Wa.

Re: Fish Finder wiring.

Post by AJ's Dad » Sat Jul 16, 2016 4:46 pm

Larry,
Thanks for the help. I sent you an email with some photos of my mounting. I should have showed it to you when you were here.

Mark

User avatar
Larry3215
Admiral
Posts: 1858
Joined: Thu Aug 02, 2012 7:02 pm

Re: Fish Finder wiring.

Post by Larry3215 » Sat Jul 16, 2016 11:11 pm

Got the pics and answered you back. Im pretty sure the problem is the step in the hull causing turbulence and bubbles as you speed up above idle.

User avatar
zen leecher aka Bill W
Captain
Posts: 815
Joined: Tue May 01, 2007 12:51 pm
Location: Moses Lake

Re: Fish Finder wiring.

Post by zen leecher aka Bill W » Mon Jul 18, 2016 7:59 am

It sounds like Larry knows his way around installing and using a fishfinder. A good person to know.

User avatar
AJ's Dad
Commodore
Posts: 934
Joined: Fri Apr 03, 2009 6:34 am
Location: Millwood Wa.

Re: Fish Finder wiring.

Post by AJ's Dad » Mon Jul 18, 2016 11:13 am

I agree. I'll move it back to my original location and see how it works. Thanks!

Post Reply

Return to “Hardware How-to's and Swap Event”