Trolling Motor Wire Size, get this!?

Get this,
My 17' Xpress came with a 46 pound MotorGuide bow trolling motor and has 10 ga wire from the battery in the back of the boat, equipped with a 40 amp fuse. It has never blown. 46 pound, 10 ga wire, 40 amp fuse.

I bought a 40 pound 12V Minn Kota Edge for another boat. I called Minn Kota and they said maximum amp draw for the 40 pound motor is 42 amps, it also says in the manual a rule of thumb is it runs about 1 amp per pound of maximum thrust. The motor instructions say to use 6 gauge wire and a 50 amp fuse. 40 pound, 6 ga wire, 50 amp fuse.

I bought an Attwood trolling motor plug and receptacle and it is only 10 ga wire(!), of course they only have 6" leads.

What gives? If I trust Minn Kota, either my Motorguide setup shouldn't work, or maybe Motorguide motors use much fewer amps? (I can't beleive that).

MY QUESTION: I'm considering a new Maxxum 24V 70 pound for the bow of the Xpress to replace the 12V. DO these newer 24V motors have 2 12V + leads and 1 12V - lead, or just two leads, implying that I have to hook my two batteries in series at the back of the boat, which would SURELY mean I have to go to 6 ga or even 4 gauge new wires all the way from the back to the front of the boat? This wire is $$$, 20' for my smaller boat of 6 gauge marine wire was easily $50 (both positive and negative, that is, 40' total)

What size wire are you guys using for your 24V 70 pound motors, and are there two or three 4, 6, 8, or 10 ga wires going from the back of the boat to the bow?

thanks,
Joe

I use two 6 gauge wires for my 70 lb MK thru a 50 amp breaker and yes the batteries are wired in series. Keep in mind that a 24V system draws ½ the current than that of an equivalent 12V system. Ohm's law.

I don't know anything about Ohm's law. You mean if you had a 55 pound thrust 12V motor, it would draw twice the amps through the wire as a 55 pound 24V motor? I guess that could make sense to me. So if 6 ga is heavy enough for a 12V 46 pound motor, surely it would be good enough for a 24V 70 pound? well shoot, that is what you got so I'm sure it is.

It's gonna be a *itch running that 6 ga wire under the rails of my Xpress boat, where the 10 ga stuff is now. Oh well, winter project maybe.

I got a 24V 50a breaker, connectors, and lugs coming for that 6 ga wire, so I'm almost ready to set up my 14' boat for fishing the 10hp lakes. I'll have better wiring in my '79 PolarKraft than in my '05 17' Xpress! for now.

Joe

Your right on track! Ohm's law is E=I/R. E=voltage, I=amps, R=resistance

i have wire dozens of trolling motors over my 25+ years of bass fishing. from 12 volt to 24 volt to 36 volt. if you use a THHN 6gauge stranded and i a 50 amp resettable breaker you should have no problems. you can buy this at most electrical supply houses. it will be cheaper than marine grade but is still very high quality. it also has a thinner tougher insulation so it is easier to pull through your boat. good luck and good fishing.

I am an electrician and I have a little pocket cheat book for finding what wire size I need for jobs where I have devices that I know the ampacity or amps of equipment. Different insulation material and number of strands in the wire gives the wire a different maximum amp rating. For example regular copper insulated with THHN has a lower amp rating than what we use on robotic welders which is MHW which I call railroad wire. Here is a link for what wire is good for what amps.

http://wiki.xtronics.com/index.php/W..._or_ampacities

Your breaker needs to be rated at or below the rating in the chart. #6 is good for 60 amps but you want to fuse it at about 50.

Hey Joe,
I have a 2001 17' Xpress X-51. I just changed my 36 pound 12 volt Motorguide motor over to a 70 pound 24 volt Minn- Kota. My boat had another set of wires already run to the back with inline fuses for 12-24 volt systems. These wires were tucked up out of the way,Had to look for them, your rig may have these as well. On my 12 volt motor the plug was wired to the black- and red+ leads, For the 24 volt motor I wired Black- and orange +. If you have a meter, check this on your boat before wiring to verify.
If you don't have the other set, wiring the batteries in series will work.
IBNFSHN knows his stuff! He has helped alot of folks with electrical problems.
Good Luck!

Crappie Stalker, I'll look for the extra wires but I think I'm out of luck there. Especially since what I have is only 10ga.

Sparky, not sure I should take advice from an electrician who calls himself Sparky!:eek:

Seriously,
My 46 pound motor draws a hypothetical 46 amps, based on manufacture rule of thumb 1 pound of thrust takes 1 amp. They are sandbagging because it has a 40 amp fuse and never blown, and it has 10 ga wire.

Now here is gets dicey. A new 70 pound thrust 24V motor should only draw a hypothetical 1/2 amp per pound of thrust because of the doubled voltage? I'm not sure if this is right...the ampacity chart you linked to doesn't specify voltage. But it does say that 10 ga wire will carry 33-55 amps. It sounds like based on that, my 10 ga wire could carry 35 amps safely at 24V. Am I way off here? Or is it a no-brainer that I have to spend at least $75 on new wire and terminals to run for the bigger motor.

6 gauge wire seems like such overkill....when the motor itself and the male/female connectors are using 10 ga.

Joe

Joe, you have got to take in consideration the max amps the circuit may need AND the distance away. Go here http://www.powerstream.com/Wire_Size.htm and page down to the voltage drop calculator. Plug in your figures and you can see what you need. You want to achieve a voltage drop of less than 1 volt. The lower the better.

Quote:

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Originally Posted by IBNFSHN

Joe, you have got to take in consideration the max amps the circuit may need AND the distance away. Go here http://www.powerstream.com/Wire_Size.htm and page down to the voltage drop calculator. Plug in your figures and you can see what you need. You want to achieve a voltage drop of less than 1 volt. The lower the better.

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Good calculator Bill.

Rule of the thumb: destination voltage (volts at motor) should never go below more than 5 percent of the source voltage (battery). This applies to any electrical ckt.

well i suggested 6 gauge wire because of a couple of reasons. 1 years ago a friend that owns a trolling motor repair shop suggested it to me. he said you get less voltage drop. when you get less voltage drop your wires do not get as hot so you dont trip your breaker. 2 my uncle is a retired union electrician (30 years) and my brother has been a union electrician for 18 years. both swear that it is worth the cost . my uncle has 2 bass boats, my brother has 1 , my dad has 1, i have 2 all have been rewired with 6 gauge wire. we never have a problem with any of them. i have fished in several new boats or nearly new, that have problems with the wiring from the factory. remember the factory is trying to make things as cheaply as possible to make profit. i am suggesting you wire yours with a little over kill to save you head aches on the water. the few dollars you save now may haunt you later at the worst time on the water. just look at it this way. you spend money on a boat , trailer, motor ,trolling motor, batteries, rods reels, jigs, minnows, and what ever else you think you need to catch fish. why not make a one time investment in the peace of mind. so you wont have to worry about wiring issues in the future. thats just my opinion, but its your money and your boat you should do what ever will make you happy. you only live once. good luck and good fishing

Quote:

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Originally Posted by Cane Pole

Good calculator Bill.

Rule of the thumb: destination voltage (volts at motor) should never go below more than 5 percent of the source voltage (battery). This applies to any electrical ckt.

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Yeah, that 5% is one of those things I knew in my before life.:eek:

I bought a Manco plug set up that 6 gauge worked in at BPS. At least I think it was Manco . I'll ck

You got some good advice Bigfish.

Marinco has recepticles for 6 gauge wire at BPS website under trolling accesories. Good luck

Guys,
thanks a bunch for taking the time to post. Excellent info.

What is finally dawning on me is that it is not that 10 ga wire can't carry the amps, it can, the motor's own wiring is 10 ga. Of course there is only a few feet of it. The problem is that a 20 foot run of 10 ga wire causes a big voltage drop. Gotcha.

'course I'm talking about two different boats here. My '79 polarkraft 1452 is getting a new 40lb Minnkota, with 6 ga wire going through a breaker, then the lenght of the boat, to a plug/receptable that is wired with 10 ga wire, into a motor that runs 10 ga wire. So, in my installation, I am using less than a foot of 10 ga wire, which won't be a problem. right?

On my 17' Xpress, it has 10 ga 12V wiring now. I will upgrade to 6 ga wire and the existing plug and receptacle also use 10 ga wire, again no more than about a foot of it. And the new motor probably uses 10 ga wire from the terminals into the guts.

It is the voltage drop stupid! I'm telling myself that again so I'll finally get it.

thanks again,
Joe

:)

Man, there is some good info on this site. I copied the charts to use at work.