Some Tolling motor questions

[tkoglin]

I just picked up a good used Minn Kota powerdrive trolling motor and since this is my first TM I have a couple of questions.

1. Is there a limit on how long the battery wires can be to run the TM? Can I mount the TM on the bow and connect it to a battery in the back of the boat that's 15' away, and if I can, What size wire should I use?

2. Are the electronics for trolling motors waterproof? My boat stays in the water all Summer long and I was wondering if it would harm the TM to leave it on the the boat or will the Summer rains eventually harm it?

Thanks  

[dale]

#1-copied from minnkota site

FAQ General

What gauge wire should I use for my trolling motor?

If the incorrect gauge wire is used, there will be a voltage loss to the trolling motor causing a decrease in power and heating of the wires.

Follow the steps and the chart below to determine the proper wire gauge to use:

Step 1.

Determine maximum amp draw of your trolling motor and round up to nearest 10.

Step 2.

Measure distance from the battery to the power outlet or trolling motor connection.

Step 3.

Take the determined length (Step 2) and multiply by two.

Step 4.

Select a gauge of wire you think may be applicable. 10 AWG is a good starting point.

Step 5.

Consult the Voltage Loss Chart to determine voltage loss per foot so you may match the wire gauge to be used.

Step 6.

Take the Determined Length (Step 3) x 2 = Doubled Length. Take the Doubled Length x Voltage Loss = Total Voltage Loss.

Step 7.

Work through equation to determine best gauge wire to be used. The best gauge selection will be matched with the lowest voltage loss.

For optimum performance, voltage loss should be between zero and one, but no greater than one.

Voltage Loss Chart AWG 5 AMPS 10 AMPS 20 AMPS 30 AMPS 40 AMPS 50 AMPS

4 .0012V .0025V .0005V .0075V .01V .0125V

6 .002V .004V .008V .012V .016V .02V

8 .0032V .0064V .0128V .0192V .0256V .032V

10 .0051V .0102V .0204V .0306V .0408V .051V

12 .0081V .0162V .0324V .0486V .0648V .081V

Voltage Loss / Ft

Example:

You want to run 20 ft of wire in your boat, and the maximum amp draw of the trolling motor is 37Amps.

Step 1.

Round up the amp draw from 37 to 40 amps.

Step 2.

20 ft of wire which is needed.

Step 3.

Take 20 ft x 2 = 40 ft.

Step 4

. Starting with 10AWG. Check the chart above for 40 amps and 10AWG.

Step 5.

.0408V is charted for the voltage loss.

Step 6.

Take 40 x .0408 = 1.632V Not acceptable over 1V.

Try 6AWG. In working through the equation it equals .064 which is under 1 volt, which is acceptable.

#2 might experence problems if you are in any saltwater enviroment

[cart7t]

Disconnect the foot control and stow it.  Those power drive foot control pedals are junk and don't like being exposed to the elements.

[JonBasser]

I don't mean to high-jack your thread, but has anyone used multi-strand speaker wire?  I believe the losses should be less than that of a solid core.

[BassNC]

Great info Dale.....I have copied that and I will plan on using that when I get my new trolling motor. I am refurbishing my bass boat and have taken all of the old wires out.....this info will be helpful when I need it.

-BassNC (Tim)

[Wayne P.]

JonBasser, whether the wire is solid or stranded has no effect on the current capacity. It's the guage that is the determining factor of voltage drop over a distance. Heavy guage speaker wire would be fine for lighting or electronics power wiring. The more strands of wire within the insulation of equal wire sizes, the more flexible it is.

[cart7t]

I know of no speaker wire heavy enough for use as TM wire.  That's a fire waiting to happen.  

[Ann-Marie]

I don't mean to high-jack your thread, but has anyone used multi-strand speaker wire? I believe the losses should be less than that of a solid core.

As pointed out, gauge for gauge the current carrying capacity is the same.

However using speaker wire, or welding cable which is very similar, is a bad choice.  In the marine environment copper deteriorates due to corrosion and oxidation.  The way to combat this deterioration is by protection and oversizing the wire so it still works despite damage.

Protection can be in the form of the insulation and covering the exposed ends.  This is helpful but not sufficient.

The next protection is to use tinned copper wire.  Each strand of the wire is plated with tin to keep oxygen and moisture away from the surface of the copper.  All marine grade wire is tinned but the speaker cables and welding cables are rarely tinned.

Finally the defense against failure due to corrosion is to reduce the surface area of the copper.  Copper corrodes on the surface.  Less surface means slower corrosion.  Ideally a solid copper conductor will have the least surface area but you risk mechanical failure due to vibration in a boat.  Regular stranded wire of marine grade is the closest alternative.  The fine strands of speaker wire and welding cable are an invitation for disaster.  They have maximum surface area and the small wire diameter encourages capillary action to pull moisture in and hold it.

[ABC123]

I just picked up a good used Minn Kota powerdrive trolling motor and since this is my first TM I have a couple of questions.

1. Is there a limit on how long the battery wires can be to run the TM? Can I mount the TM on the bow and connect it to a battery in the back of the boat that's 15' away, and if I can, What size wire should I use?

2. Are the electronics for trolling motors waterproof? My boat stays in the water all Summer long and I was wondering if it would harm the TM to leave it on the the boat or will the Summer rains eventually harm it?

Thanks

1) A) You can......but why?? By the time you buy heavy gauge wire, connectors, and take the time to install it, you could have bought a trolling motor battery and box, put it in the front of the boat, and been fishing. It will work to use one battery for everything, but your better off, in the long run, to buy a quality deep cycle battery for all the boats power, and use a seperate starting battery just for the motor.

You could just add the second battery for the TM, and leave the rest alone. Odd's are your going to need at least 40ft of 8 gauge wire. I bought 6ga wire for about $1 per foot last year, I'm sure 8 is in the 80-90 cent range. Figure $35 for wire, $4-5 for connectors and/or splices, plus time to install.....For about $50-60 you could get a decent battery and box.

 

[Catt]

Here are a couple tips shrink wrap or liquid tape all connections; if done properly this will environmentally seal the connection.

[tkoglin]

"1) A) You can......but why??"

I'll be mounting this trolling motor on the front of a pontoon boat and was thinking of mounting the battery inside the rear benchseat for less clutter up front and it would keep the battery out of the way of anyone sitting the  front swivel seat.

Judging by the cost, I'll probably just go the battery box route and just take the battery off the boat when we use the pontoon for swimming or leisure.