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jwmiller33

yet another battery question (my apologies)

14 posts in this topic

Ok, so heres the deal. I originally had a 35 hp Johnson tiller and the lower unit blew out on me and now the motor I am getting is a newer 35hp Johnson long shaft tiller, only difference is this one is electric start and my old one was a pull start. What this means is that how I originally had designed and planned my boat is not going to work because I have one deep cycle in the back for the trolling motor, and then I have another battery up front in the front storage that runs the depth finder and lights. I know the second battery in the front just for the depth finder and lights is a little excessive, but I really liked the idea of having the weight of a battery in the front of the boat for safety and stability purposes (on my 1985 S-16 Lund). So I am pretty sure I have two deep cycle marine batteries. Now, I need to purchase a starting battery for the electric start motor, right? So does this mean I am going to have 3 batteries on board now?

I heard that you shouldn’t run the graph off the same battery as the trolling motor, which is another reason I had gone with 2 batteries over one. Can I have my trolling motor and lights hooked up to one battery in the front? And then have the battery in the back be the starting battery and run my graph off of that?

Here are pics of my two deep cycles I have right now:

DSC00339.jpg

DSC00340.jpg

DSC00342.jpg

DSC00341.jpg

Can you guys give me some advice on how I should do my batteries now that I need a starting battery? I am thinking about just getting a starting battery and having that in the back along with my trolling motor battery and keep the graph and lights running off the one in the front. I don’t really care about the added weight as my motor is plenty big for my boat, I just really want/need to have one battery up front for weight distribution means. I really don’t want to have to run the trolling motor chord all the way to the front, as I already redid my entire boat project and I don’t want to have to tear it up and redo the wiring.

How many cold cranking amps do I need for a starting battery? If I was going to get a third battery and its only job was for starting the motor, what kind of battery should I go with? Thanks for your help guys and sorry for yet another battery question.

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would it be a problem if i had the starting battery way up front and extended the chords from the motor to reach it? I know you get some sort of voltage drop per every foot of wire you have when its that thick of a gauge of wire. thanks for your help guys

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My previous boat was a Lund rebel and everything ran off one battery in the back so you shouldn't have any trouble using your rear battery to start your motor.

They put batteries in the trunk of drag cars and use them to crank high compression big block motors so the voltage drop is neglible, especially a light duty application like yours.

Good to hear you will be back on your feet for the weekend. Are you keeping the old motor for parts?

Steve

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the battery i have in the back is the trolling motor battery. i thought if anything, i should run the starting battery off the front battery that is currently only running the graph and the nav lights.

when i use my trolling motor all day, my battery gets pretty run down, and i dont know if there would be enough juice to start the motor. dont you think this would be the case?

are my batteries that I have right now sufficient for being a starting battery?

thanks for all your help steve.

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Yes, either of those will start a 35hp just fine. I would use the back battery for the starter and your lights and graph, and the front battery exclusively for the troll motor. Should work jsut fine, and you won't have to extend the starting battery cables, something you don't want to do unless absolutely necessary.

Right now I am using a 5 year old car starting batt for my 25hp evinrude, and run the graph to it on my pontoon. Battery before that was a 10 (yes, ten) year old deep cycle. It doesn't take much to start those smaller hp motors.

Good luck jw! Boats are always some task for us, huh? smile

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Unless you using your trolling motor non-stop all day without using your outboard to get from place to place, it is actually beneficial to have your OB hooked to the same battery as it will provide a small amount of charging from the alternator. Also it doesn't take much juice to start a small OB and a big deep cycle should have plenty of power even after extended trolling sessions

Does the new motor have a manual start at all? Otherwise you could put the rope starter housing on the new motor and use the old hood that has the pull start hole in it in the event that you did wear down the battery too much.

Or you could hook up both batteries in parallel which keeps the system at 12 volts but adds "juice" (not sure the official electrical term) to your system.

Steve

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I have a question since I am not a marine type person. I have used a divider to keep power from the starting battery going into the other battery. You can hook your motor to the start battery however all your other stuff could go on the other one so it is isolated from the starter battery. That way when the accessory battery goes low, your start battery will be ok. When charging, it will allow current to enter both batteries. Would this be something that would work in a marine application? And use of filter of twisting of the power/ground to the fish finder to keep the RF down. Is this done? Sorry for the question. Jeff

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right now, the way i have the boat wired, the graph power wire and lights power wire both run to the front storage of my boat, here:

DSC00263.jpg

i have a spot underneath my seat where the trolling motor battery goes, here:

DSC00278.jpg

it would be easiest to wire the Johnson motor to my trolling motor battery, then I wouldn't need to fool around with any re wiring (such as wiring the trolling motor all the way up to the front battery, and run the lights and graph power wires to the back battery and re mount the lights switch).

are you sure this it is fine for me to hook my 35hp Johnson AND my 55lb MinnKota trolling motor to the same battery? Even if I use the trolling motor all day?

Are either of these batteries sufficient to be a starting battery? i bought them as deep cycles and not starting batteries, but i read somewhere that that doesnt matter?

thanks guys i really appreciate the help

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Never heard that you couldnt use a DC to start a motor. Have done it for years and my batteries always last for several years.

I used only 1 DC to run depth finder, lights, 55# Minnkota, and start 25 Suzuki on my previous boat and never had a problem.

Steve

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are you sure this it is fine for me to hook my 35hp Johnson AND my 55lb MinnKota trolling motor to the same battery? Even if I use the trolling motor all day?

Are either of these batteries sufficient to be a starting battery? i bought them as deep cycles and not starting batteries, but i read somewhere that that doesnt matter?

thanks guys i really appreciate the help

If you hook up both starting and trolling motor to same battery, you WILL be pull starting that outboard. Maybe not if you only use it a little bit, but it WILL happen. Never put both on the same battery, unless you know you will not be using the troll motor hardly any at all, and even then it is bad idea because you will need to charge the starting battery after each day, as that little alternator on that 35hp won't catch up, unless you simply drive at WOT for an hour after using the troll battery.

Do as I mentioned above, or ask someone else, and then do as I mentioned above when they give you the same advice wink

I can wear out a new fully charged 12v group 27 in a day of fishing with only the troll motor hooked up. In fact is happened to my stepson just on Saturday (it was windy) but our 24v on our bigger boat didn't wear out. Then you need to charge it. If you want to try it with one, I suggest getting an on board charger, just to make life a bit easier. They are the best thing for a boat and batteries.

Good luck.

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Easy answer: Replace the battery in the back with a dual purpose battery for the trolling motor and starter and you are all set to go smile

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A deep cycle battery is intended for extended periods without a lot of amp draw. Still your 35 hp starter is going to be fine with a deep cycle.

Question is sharing the battery with the trolling motor.

Yes you will probably have days where you'll have drained the battery enough not to turn over the starter. Just because you have electric start doesn't mean you can't pull start it. After all you pull started your old 35.

Three batteries would be out of the question as far as I'm concerned.

Mounting both batteries in the stern is an option but IMO your boat is too small and that extra weight in the stern will be noticed on hole shot and top end.

The deep cycle in the bow is sort of wasted by only powering lights and sounder.

I'd either.

Get a bow mount.

Run 6 gauge wire back to the stern for either your starter or trolling motor with a circuit breaker at the battery.

This would be wired directly to the trolling motor or to a termination block with a connection to the outboard. Might even be best to bring that to an accessory panel with breakers for future accessories.

Or keep it all as is and share the battery with starter and trolling motor and see how it works out.

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I have a 16 footer with a 35 evinrude elec. start, I leave the humminbird hooked up to the starting battery and use the deep cycle for the trolling motor. I haven't had a problem yet with anything. I've got the starting battery in the back and the deep cycle in the middle of the boat with some extra 6 gauge wire running back to the trolling motor. It seems to work just fine.

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went out two days in a row with the new motor and i just had it wired up to the battery in the back (same as the trolling motor) and i didn't have a problem with it either day. i was out on island lake 2 days ago in 30 mph winds and 3 foot rollers, the traditional island lake white caps, so my trolling motor was being used heavily and it still started fine.

i always have the pull start option too, so i think i am fine for now, but i intend on running 6 gauge wire from the motor to the battery up front (battery currently running graph and lights), and i dont think i will ever have to use the pull start...

i think the best solution would be for me to buy an on board charger, which is exactly what i wanna do. how big of one do i need for my situation/set up? i know there are all different sizes of them, and i have no idea what kind i need to buy.

thanks much

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