# Trolling Motor Size Vs. Voltage



## gajet31 (Apr 7, 2014)

I currently run an older Motorguide 12 volt trolling motor with 54 lb of thrust. This motor is powered by a deep cycle trolling battery, used only for this trolling motor. I also have a cranking battery that powers my outboard, lights, bilge, etc... 

Due to the current of where I fish, I need to get a larger trolling motor. I am looking for something with more than 54 lb of thrust, but I cannot justify the weight of adding a second battery just for the trolling motor. My boat is extremely weight sensitive.

I guess my options are: A) find a larger trolling motor (i.e. 75 or 82 lb of thrust) that will still operate with 12 volts allowing me to stay with 1 battery for trolling or B) upgrade my trolling motor to a larger size and voltage (24 volts) and find a way to rewire my rig so I don't have to purchase a 3rd battery. Is this possible? Thoughts?


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## kofkorn (Apr 7, 2014)

The reason for moving from a 12V system to a 24V system has to do with power draw. Your power (thrust) will be determined by how much voltage you have and the current draw that you can supply. Typically on a 12V system, you are looking at about 1 amp per lb of thrust. So your current 54 lb motor is drawing about 50A of current.

If you went to an 80 lb motor on a 12V system (I doubt you'll find one that exists), you would be drawing about 80A. I would guess that your current wiring is rated for 50 or 60A continuous. If you did not upgrade your wiring, you will be drawing too much power through it and would experience a very significant voltage drop. In addition, the wire will heat up and could potentially melt the insulation and cause a short. 

Now on the other hand, if you go to an 80 lb thrust on a 24V system, you would only be drawing about 40A through the wiring. Other than adding a jumper wire between the two batteries and a new 3 bank charger, you wouldn't need to do any upgrades to your wiring. Most wiring is rated for 300 - 600v, so no upgrade would be needed. You would have to do much more of a wiring upgrade to get 80A @ 12V than 40A at 24V. 

Now for the weight, instead of two Group 24 batteries, you could save weight by looking at two smaller batteries similar to this: https://www.ecomelectronics.com/prodinfo.phtml?id=3315796&gclid=CNy85bTszr0CFdBqfgodRRAASQ

They won't last nearly as long as group 24's but would be much lighter. I can guarantee you that even with two of these smaller batteries, you will have less run time than your single group 24 on a 12V system. The would probably last about 1/4 as long as your current setup.

Honestly, if you are having a problem with the current and need a stronger motor, I would go with the 24V system with a minimum of two group 24 batteries and find other ways to lighten the boat instead. You don't want to be out in the current when your battery dies, and with a 24V system, you won't be able to go to your cranking battery as a backup. 

Good Luck!


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## mphelle (Apr 7, 2014)

Describe your rig, (size, motor, average weight you carry). Post some photos if you have any.


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## redbug (Apr 7, 2014)

As your rig stands now you have 1 deep cycle battery and 1 cranking battery 
if you try to join 2 different size batteries you will wind up shortening the life of both 
I run a 109 lb thrust trolling motor when I first got it I had a 19 ft boat and only ran 3 size 27 group deep cycle batteries 
one was also hooked to my starting circuit this worked fine until I went to my 21 ft boat and 4 batteries 
just make sure the 2 batteries are the same size and age for the best results 
its not IDEAL but it will work


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## ccm (Apr 7, 2014)

If weight not $$$ is your issue. I'd look into the new type lithium Ion batteries. You can hold one above your head one handed their extremely light, last for years but they are expensive. Might be worth it/however long your going to keep your boat. The most powerful 12 volt motor I know of was a MotorGuide Brute 767 ( no longer made ) It was a 12/24 volt model with 67lbs of thrust.


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## redbug (Apr 7, 2014)

[url=https://www.tinboats.net/forum/viewtopic.php?p=347827#p347827 said:


> ccm » Mon Apr 07, 2014 5:09 pm[/url]"]If weight not $$$ is your issue. I'd look into the new type lithium Ion batteries. You can hold one above your head one handed their extremely light, last for years but they are expensive. Might be worth it/however long your going to keep your boat. The most powerful 12 volt motor I know of was a MotorGuide Brute 767 ( no longer made ) It was a 12/24 volt model with 67lbs of thrust.


 CCM... do you read this board????? $$$$$$$$$$$$ is always an issue lmao
I thought I was bad when I dropped $700 on 3 agm batteries


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## ccm (Apr 7, 2014)

All I'm saying is that lithium batteries might be worth looking into. They are quite expensive but they recharge quicker, lighter, and last for about 10 years according to what brand you go with. I know in a perfect world they would cost the same as regular deep cycle batteries but sadly this is not a perfect world. I'm just hoping that technology keeps progressing so that I can afford to have a 36 volt system that weighs less than 150lbs one day. With batteries and trolling motors everyone has different needs, and budgets to go by. But as far as high thrust 12 volt motors go they punish batteries. Mercury in the early 90's made the thruster ( AKA the coffee grinder ) but it was found that you had to have two batteries wired in parallel for this motor and it still drained the batteries. If you need more thrust its looking like a 24volt system might be your best bet. Any battery size less than group 24 wont last as long as a 12 volt motor with a single battery. 1 more thing how long and wide is your boat. A picture might help to decide where the best weight distribution would be. I hope any advice given will help you with your dilemma. Also what type of prop do you have on your MotorGuide? I have found that their 2 blade power prop will give more thrust vs their 3 blade machete prop.


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## gajet31 (Apr 8, 2014)

My rig is a 1648 SC with a 50 hp jet at the powerhead. I have a similar post on the jet boat forum about it and one user recommends using a Trollbridge24. The information is below in the link, but it looks like it would work perfect for my situation. It basically connects my existing cranking and trolling batteries to form a 24v power source for a larger TM, but also separates them for when I need to crank my outboard. It also seems to have a few features such as a recharging system when the outboard is running.

Anyone have any experience with these? Reviews or testimonials?

Thanks,


Link to Trollbridge24 info below:
https://www.yandina.com/troll24info.htm


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## FerrisBueller (May 14, 2014)

Somewhat of an old topic, and I think you got a lot of great responses. To go along the lines of ccm, the issue is basically on that weight to cost balancing act. You could get some nice agm batteries to do the trick no problem, but at a high cost. Heck I think we'd all love to lose some weight in the power dept but for most of us we need the cheaper option. I'd be hesitant to link your tm and cranking batteries, you dont want to run it too low and be stuck on the lake. And I'm not sure of your setup but usually the 2 power supplies aren't next to eachother.


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