Boat Electronics

[Sam]

Help me figure out my electrical set-up, please. I've got a 17' aluminum bass boat with a 50 hp Suzuki 4-stroke outboard and a 40 lb. thrust Minn-Kota trolling motor. On the console I've got a Humminbird 597ci depthfinder (wired to the main battery circuit), and up front I've got a Eagle Fish Mark 320 depthfinder (wired to the trolling motor circuit).

I run two deep-cycle marine batteries, both brand-new. They're both the same, "Fish Hunter" HD27DC, 845 CA, 675 CCA. One battery starts the main motor and powers the instrument panel, boat lights, livewell and bilge pumps, and the Humminbird on the console. The main battery gets charged by the outboard motor when I'm running. The other battery gets charged only at home and it runs the trolling motor and the Eagle depthfinder up front.

My problem is that the Humminbird apparently has a feature that causes it to freeze up when there's a drop in voltage. About 3/4 of the time when I start the outboard motor, the Humminbird freezes. It doesn't just turn itself off (which wouldn't be so bad). It looks like it's off but there's actually a little bit of light coming from the screen and all the buttons, including the Power button, quit working. Then I have to pull the depthfinder from the mount, put it back on, and go through the start-up routine. Next time I start the outboard, same thing.

It's a real pain to have to stop, stand up from the driver's seat, press the release bar, pull the depthfinder from the mount, then stick it back on. Sometimes the boat is bouncing around in waves or I'm in some kind of boat-handling situation that needs my attention, and having to do this - sooner or later I'm gonna accidentally drop that depthfinder in the lake. Both batteries have plenty of power, it's just the power drop when I start the motor that causes this.

The obvious solution would be to connect the Humminbird to the other battery's circuit, but I think that would be even worse. My Eagle depthfinder up front dims when I use the trolling motor on the higher speeds. In fact late in a fishing trip if I've been on the trolling motor a lot and that battery's getting low, the Eagle depthfinder quits working. That's not a big problem, as it takes a long fishing trip and a lot of trolling motor use to cause that - but since the Humminbird is so sensitive to power fluctuation, I think it would act even worse on that trolling motor circuit.

I don't have room to add a third battery for depthfinders only, so that's not an option.

Does anyone here know how to fix this? Thanks.

[Jerry Rapp]

I really don't know the technical answer, and I am sure Wrench or someone else will come along soon with a better answer, but I think you would be better off of getting a regular cranking battery for the OB and electronics. A deep cycle is not designed for sudden power draws.

[Troy Gregg]

Jerry hit the nail on the head, deep cycle batteries don't do well with a sudden demand for juice. I would put the trolling motor on its own circuit as that will eliminate any electrical drainwith your eagle unit. The Humminbird is a slightly more delicate situation, you will probably need to upgrade to a dual purpose battery with a highe cranking amp and reserve capacity to maintain enough amps to power everything

[Sam]

Thanks, fellas. Uh-oh, that's what I've suspected for some time, that I ought to have the trolling motor on its' own deep-cycle circuit and everything else on the boat, including the two depthfinders, on a cranking-battery circuit.

I ran two Delco M27 deep-cycle batteries for years and as they both got pretty old and weak last fall I had the same problem with the Humminbird freezing up, but not so often. It got to where neither old battery would take a good charge so I waited all winter to replace both of them in the spring. I replaced them both about a month ago with these Fish Hunter HD27 marine batteries, so my batteries are both brand new. Since the change, the Humminbird freezes up most every time when I start the outboard.

Thing is, I ASKED the guy at the battery shop (who seemed to be an expert) if I shouldn't be running a cranking battery on the main circuit and a deep-cycle marine battery on the trolling motor circuit. He said no - it was fine the way I had it, and besides, running identical marine batteries allows me to switch them if I need to. I believed him.

So, since I hate to replace a brand-new $90. marine battery right now with a cranking battery, I've got a whole 'nother question:

What if I put the trolling motor on a circuit all its' own with one deep-cycle battery serving it? I know that needs to be done, and this battery would be charged at home between trips with a battery charger.

Second circuit = everything else on the boat EXCEPT the two depthfinders. This would start the outboard motor and power the lights and livewell and bilge pumps. For now, this would be the second deep-cycle marine battery and I know that's not ideal - I'll replace that one with a cranking battery in 3 years or so when it needs replacement. But this is a NEW battery and I'd like to get my use out of it. Marine batteries have worked fine for me in the past for starting, etc. as my outboard is only 50 hp. This battery gets charged when the outboard is running, of course - the alternator always shows 13/14 volts on the gauge even at low rpm's.

THIRD circuit. What if I get a third, small, auto-type battery to power the two depthfinders only? I don't have room where my batteries are at the back of the boat, but I could easily put a plastic battery box in a front-deck compartment and reach both depthfinders with short wire runs under the front deck (with in-line fuses in both, of course). This battery would get charged separately at home between trips.

The question: How much battery would it take to power only those two depthfinders for about 12 hours? Not much, I'm guessing. If there's still such a thing as a $35-$40 12-volt battery for small tractors and such, I bet that would do it. Does anybody here know? Thanks.

[Troy Gregg]

Sam your idea will work but you still want to make sure that your small mower battery is a deep cycle as well the electronics you are running do not demand a lot of juice thankfully. The big screen units would eat a small battery in a matter of a few hours at most.

As long as the battery has the minimum required cranking amps it will work for cranking, it just wears it out a faster rate.

Hope this helps

Troy Gregg

[dave potts]

You can get small marine deep cycle batteries at an Academy store. Wal-Mart used to sell them but haven't in years.

[Goggle-Eyed]

I would think it would be much easier to list the brand new battery for sale at $50 and then take that money and go buy the proper battery. A small battery will cost $30-40 and not be ideal situation. if you sell yours for $40-50 you would be at the same money and less headache!!!

[fullmoon]

What if you power off the humminbird before you start the motor and power back up after its started.

[Sam]

What if you power off the humminbird before you start the motor and power back up after its started.

Exactly! I went fishing today out of Cape Fair (caught some crappie) and I soon figured this out. I just got on here to post the "solution" and you already had it. When I start the outboard motor I'm sitting in the driver's seat, so all I've got to do is turn off the Humminbird, start the motor, then turn the depthfinder back on. Duh.

Thanks for the help, though, guys. I'll get the Eagle up front off the trolling motor circuit, and while my new batteries are still good I'll simply turn the Humminbird off and back on when starting the outboard. In time, the first deep-cycle battery that conks out will be replaced with a cranking battery and then I'll be all back to normal.

Sometimes I'm a little slow.