Trolling Motor Wire Size and Breaker Guide

Wire size and breaker chart

Most bow mounts come with leads a few feet long. On a bass boat the batteries sit near the back, so you run an extension up to the front deck. That extension is where people get the size wrong.

Wire sizes in AWG, from Minn Kota's trolling motor wiring and battery guide. Distance is one way, from the batteries to the motor leads. The chart assumes 105 °C wire, no more than two wires bundled together outside the engine space, and no more than 3% voltage drop at full power. Past 25 feet, Minn Kota says to see a marine technician.

One heads-up on the 101 lb row: by the voltage drop formula below, 8 AWG at 46 A drops about 3.3% at 20 feet and 4.2% at 25 feet, a bit over 3%. That row is the same as Minn Kota's older chart, which allowed more drop. If you want to stay under 3% on a 101 lb motor at 20 to 25 feet, use 6 AWG. That's what our Wire Size Calculator will show you.

A lower AWG number means thicker wire. 2 AWG is much heavier than 8 AWG.

Older copies of this chart, like Minn Kota's 2023 battery chart PDF, show thinner wire because they allowed 5% voltage drop. The current chart allows 3%, so use it. Other brands publish their own charts, and a forum thread on iboats noted one MotorGuide manual lists a 50 A breaker where Minn Kota lists 60 A. Always follow the manual for your motor.

Not on the chart? Our Wire Size Calculator has trolling motor presets and works for any amps and distance.

How the chart works

Every foot of wire has a little resistance, so some voltage is lost on the way to the motor. That loss is called voltage drop. The motor gets less than the battery puts out, so it runs weaker, and the wire turns that loss into heat.

The standard boat formula, used by ABYC (the group that writes boat wiring standards) and wire makers like Ancor, gives the wire thickness you need in circular mils (CM), a measure of a wire's cross-section:

CM = 10.75 × amps × round-trip feet ÷ allowed volts dropped

Example: a 55 lb, 12-volt motor drawing 50 A at full power, with the batteries 10 feet from the motor.

• Round trip: 10 feet out and 10 feet back is 20 feet.
• Allowed drop: 3% of 12 volts is 0.36 volts.
• CM = 10.75 × 50 × 20 ÷ 0.36 = 29,861 circular mils.
• 6 AWG is 26,240 CM, too thin. It would drop about 3.4%.
• 4 AWG is 41,740 CM. It drops about 2.1%, so 4 AWG it is, the same as Minn Kota's chart.

Our Wire Size Calculator runs this same math, then checks that the wire can safely carry the breaker's rating under the Coast Guard's ampacity table (33 CFR 183.425). For example, 8 AWG wire rated 105 °C is good for 80 A outside the engine space, which is more than a 60 A breaker.

That's also why 24 and 36 volt motors get away with thinner wire. 3% of 36 volts is 1.08 volts, three times the drop you're allowed at 12 volts, at about the same amps.

Breakers and fuses

The breaker protects the wire. If something shorts, it cuts the power before the wire overheats and starts a fire. Minn Kota says each hot wire needs a manually reset, trip-free breaker or a fuse sized for the motor. Trip-free means it will trip even if someone is holding the lever.

Where it goes

On the positive wire, as close to the battery as you can. Under the ABYC standard, as Blue Sea Systems explains it, protection on a wire connected to a battery should be within 7 inches of the battery. If the wire is fully covered in a sheath or conduit, that can stretch to 72 inches. Blue Sea also says to keep breakers and fuses out of the battery compartment itself, because of corrosion and battery gases.

On a 24 or 36 volt setup, the breaker goes on the red lead where it meets the last battery's positive post.

Breaker or fuse?

Either works if it's sized right. Most people pick a breaker for a trolling motor because it can be reset on the water, and many double as an off switch. An iboats forum moderator put it simply: use a breaker or a fuse, not both. Shop our breakers or fuses.

Why it trips

Minn Kota's max amp numbers happen only for short stretches, at full power. A breaker that trips often usually means the motor is working too hard. Common causes are weeds wrapped around the prop, a low battery, or a loose or corroded connection. Bass Pro notes tangled weeds can make a motor overheat.

Hooking up 12, 24 and 36 volts

Turn the motor off and set the speed to zero first. Minn Kota warns that wiring a 24, 36 or 48 volt system wrong can make a battery explode. Never connect the positive and negative posts of the same battery.

12 volts, one battery

1. Red lead, through the breaker, to the battery's positive post.
2. Black lead to the battery's negative post.

24 volts, two batteries in series

1. Jumper from battery 1 positive to battery 2 negative.
2. Red lead, through the breaker, to battery 2 positive.
3. Black lead to battery 1 negative.

36 volts, three batteries in series

1. Jumper from battery 1 positive to battery 2 negative.
2. Jumper from battery 2 positive to battery 3 negative.
3. Red lead, through the breaker, to battery 3 positive.
4. Black lead to battery 1 negative.

Steps from Minn Kota's wiring and battery guide.

Check your work with a meter before you connect the motor. Across the red and black ends you should read about 12, 24 or 36 volts. Batteries in a series set should all be the same make, type, size and age. Our trolling motor batteries guide covers why.

Plugs, switches and parts

A plug at the bow makes it easy to pull the motor off for storage or service. Minn Kota says to keep the polarity right if you add one, so red always meets red. Pick a plug rated for more than your motor's max amps, and check that the wire you're using fits its terminals.

Minn Kota also says to disconnect the motor when it's not in use and while the batteries charge. A manual reset breaker or a battery switch on the positive wire does that with a flip.

A typical bow-mount extension needs:

• Red and black marine wire in the size from the chart, long enough for the full run
• A breaker in the size the motor's manual calls for
• Heavy-duty ring terminals sized to the wire and the battery studs, plus heat shrink
• Jumper cables for series setups, one size heavier than the motor leads
• Loom or conduit, and clamps to keep the wire from rubbing

Ancor's marine wire, for example, uses tinned copper strands for corrosion resistance and is rated 105 °C dry, which matches the chart's assumption. Federal rules (33 CFR 183.425) require boat wiring to be insulated, stranded copper, so leave solid house wire at home.

Common mistakes

• Measuring the run the long way. Minn Kota's chart uses one-way distance from the batteries to the motor leads. The formula above uses round trip. Don't double it twice, and don't forget to double it once.
• Reusing old, thin wire when you move up to a bigger motor.
• Jumpers too small. They carry the full motor current, so they need to be heavier than the leads.
• Breaker too big "so it stops tripping." That leaves the wire unprotected. Find out why it trips instead.
• Loose or corroded lugs. Minn Kota says to keep battery posts tight. A bad connection drops voltage like thin wire does.
• Feeding the trolling motor through a fuse block. Its current is far too high for an accessory block. Give it its own circuit. See our fuse block guide for the electronics.

Questions people ask

What size wire do I need for a 24 V trolling motor?

For Minn Kota's 80 lb, 24 V motor: 8 AWG up to 5 feet, 6 AWG for 10 to 15 feet, 4 AWG at 20 feet and 2 AWG at 25 feet. A 70 lb motor can go one size thinner on most runs.

What size breaker for a 55 lb trolling motor?

Minn Kota lists 60 A for its 50 and 55 lb, 12-volt motors, which draw up to 50 A. Check your own motor's manual, since other brands may differ.

Can I use a fuse instead of a circuit breaker?

Yes. Minn Kota accepts either one. A breaker is handier because you can reset it on the water and use it as a shut-off.

Does the breaker go on the positive or the negative?

The positive, close to the battery. On a series setup, that's the positive post of the last battery, where the red motor lead connects.

Why does my trolling motor breaker keep tripping?

Usually because the motor is pulling more than normal: weeds on the prop, a low battery, a bad connection, or running flat out for a long time. A breaker that's too small for the motor will also trip. Match it to the manual.

Can I extend the leads on a 30 lb trolling motor?

Minn Kota says not to, because it hurts the motor's performance. Mount the battery close enough to reach the stock leads.

What gauge jumper cable between trolling motor batteries?

One size heavier than the motor's lead wire, per Minn Kota. If your leads are 8 AWG, use 6 AWG jumpers.

Is thicker wire than the chart OK?

Yes. Thicker wire drops less voltage, so the motor gets more power. The only costs are price, weight and making sure it fits your plug and terminals.