I know this horse is beaten but:

I'm going to be putting a 24v minnkota where a 12v motorguide was. Do I need to re-wire the boat for a heavier gauge? I don't remember what the concrete information is on this subject.

Just to be safe I would re-wire it. But if you are smart about it, before you take the old wires out I would attach the new wires and pull it through so you don't beat yourself up trying to get the wires in the right spot. Any way to help you stay out on the water with fewer mishaps or break-downs is the way I will always go (money allowing)

Why? What's the risk / reward?

Risk:  If the old wiring is weak and not meant to hold 24v it will get extremely hot and burn up and you risk catching your boat on fire from the inside out.

Reward: More time on the water and less to worry about.

If it were me I would change the wiring. Some wires do not hold but a certain amount of current and when you try to run to much current through a small cable it can burn the cable or burn up your new trolling motor.

I'll have to check what gauge my boat has. Thanks man.

Anytime!!!

you do not have to worry about rewiring it. The wire in your boat is probably good for 300V maybe even 600V. Plus is it not the wire itself that has that rating it is the insulation. The wire will carry any voltage you can put to it. it is whether or not the insulation will contain it.  

The thing you have to worry about is current. A 24V motor of the same thrust as a 12V will draw half the current. So the chances are your 24V motor will draw less current than your 12 volt. If you have 6 or 8 gauge wire i would not worry about it.

Is the wire marked, or do I need to find a section of 6 and compare. I hear a lot that older boats (mine's a 98) had 10 gauge.

The wire is usually marked. if not you can measure the diameter of the copper itself. here is a chart

http://en.wikipedia.org/wiki/American_wire_gauge

Team-Doughterty,  Right On!  Ohm's Law is such a simple equation that it should be taught in Elementary School.   ;D 8-)

Team-Doughterty, Right On! Ohm's Law is such a simple equation that it should be taught in Elementary School. ;D 8-)

;D

That chart makes my face hurt from brow furrowing.

That chart makes my face hurt from brow furrowing.

It is pretty easy. For example to find watts; you can square the voltage and divide by resistance in Ohms, Or you can square the amperage and multiply by the resistance in Ohms. Or, you can multiply the voltage by the resistance. That is three ways to find The wattage of an electrical device. These formulas work for AC or DC devices.

On some charts the use I instead of A for amperage and P, for power, instead of W for watts.

So how does this relate to you? Easy. Lets assume, and most people use this formula, that a 12 volt trolling motor draws 1 amp for each pond of thrust. So a 50LB thrust 12 volt motor draws 50 amps. so using ohms law 50 amps X 12 Volts = 600 watts.

So if you have a 50LB thrust 24 Volt Motor it will still "consume" 600 watts of power. so using Ohms law again. you take 600 watts divided by 24 volts and you get 25 amps of current. Half the current draw of the 12 volts motor.

Therefore you can run a 100LB thrust 24V motor on the same wire as a 12V 50lb thrust because they will both draw 50 Amps.

Now my head hurts ;D

You need a chart you can remember.  I teach my students to remember the word OVA as in over the hill.  If you write these letters as a hill you get:-

   V

-------

O     A

To get the formula for Ohms, Volts or amps just cover that symbol up and the remaining two are the formula.

Example to find the ohms in a circuit cover the O and you are left with V/A or volts divided by amps.

How about what year and make of boat is it?

It's a 98 nitro. I hooked everything up today. 6 gauge throughout  already.

I did run into something else. When I engaged the motor, it seemed pretty sluggish, like it would if it were low on juice. I'm almost positive both batteries had a good charge.

The only thing I can think of is either: low batteries and I just need to wait until they charge. I did re-use the 12/24 plug from the old motor. The negative wire stayed in place and the positive was switched from the 12v terminal to the 24v terminal.

What else could be culprit?

are your batteries hooked in series, 24v, or parallel, 12 volt,? If you have them hooked positive to positive and negative to negative that is parallel and will only deliver 12 volts to your trolling motor. That is half of its rated voltage and it will run very slow.

See below. change "to charger" to "to motor"

You need to hook your batteries in series.

They are hooked in series.

Are there two or four wires run to the front plug?

Well,

The good news is that the whole thing is fixed. The bad news is that I'm an idiot.

I had labeled the wires for the outboard as the wires for the trolling motor. The outboard was hooked up to a 24v series. The trolling motor was hooked up to one battery. Along with my graphs. Everything runs like a champ after a little re-labeling.

Bring on the ribbing. I deserve it.

"F"

Hopefully your outboard did not suffer any damage from that. I bet the starter motor turned real fast though.

Well, the outboard runs fine. I hope it didn't burn anything up also......