However, it’s easy to get confused about certain aspects of the process like what trolling motor wire size you should use for best results.
There are many variables to keep track of when selecting a size for your trolling motor wire gauge. This includes the motor’s amperage, motor voltage, type of wire gauge, the distance between the battery and motor, and more.
Photo by cottonbro studio
Failing to consider these factors can cause you to choose a wire gauge that’s inappropriate for your trolling motor, resulting in significant damage.
To help you avoid bad outcomes, this article is going to guide you through how to choose the appropriate wire size for your trolling motor.
- Understanding Trolling Motor Wire Sizes
- Factors to Consider When Determining Wire Size
- Wire Size Calculation Methods
- Common Wire Sizes for Trolling Motors
- Wiring Installation and Best Practices
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Before you can figure out which wire size will fit the requirements of your trolling motor, you need to understand what certain technical terms mean, as well as their significance in trolling motor installations.
Wire gauge also known as American Wire Gauge (AWG) is a measurement that refers to the physical size or diameter of a wire and the current capacity that it can safely carry. It also determines the weight per unit length and electrical resistance of the wire.
Wire gauge is expressed using a fixed numerical classification that is inversely proportional to the diameter of its conductors.
This means that if the wire gauge number is high, it will have a narrower diameter so the wire will be thinner while wires with a lower gauge number will be thicker or larger in diameter.
A good rule of thumb to keep in mind is that the longer the length of wire you require, the lower the gauge number you’ll need because the wire you choose has to be thick enough to make up for the additional length.
The gauge wire is available in two variants that you’ll have to pick from after determining the correct wire size for your motor: regular grade wire gauge and marine grade wire gauge.
Photo by Mikael Blomkvist
The regular grade wire is cheaper and suitable for a variety of general functions depending on how small or big your boat is. However, if you’re willing to invest a little more to get a high-quality wire, then the marine grade wire gauge is the best option.
It’s very durable, easy to install, and offers great sound insulation. And since it is built following AWG standards, it is 10% to 12% bigger than the regular grade wire that follows SAE standards, making it ideal for marine applications including wiring of trolling motors.
There’s a direct relationship between the size of the wire that will be suitable for your trolling motor and the amperage of the motor as well as the distance between the motor and battery.
The maximum amperage of your trolling motor will determine the length and diameter/thickness of your wire gauge. The higher the amperage the longer and thicker your wire would have to be.
Photo by cottonbro studio
The last thing you want is to end up using a wire that can’t carry and transfer the current requirements of the motor plug and battery. This can easily result in the wire melting due to overheating or the trolling motor shutting down.
The distance between the motor and battery also matters a great deal when ascertaining the perfect wire size. Most people like to position their battery in spots where it won’t get in the way of other items you store on deck and where it’s less likely to be stolen or exposed to direct sunlight.
Consequently, trolling motor batteries often get placed far from the deck which can create quite a bit of distance between it and the trolling motor. If you follow the same pattern, you’ll need to compensate for the distance by increasing the wire gauge length you have to use.
Fitting your trolling motor with the wrong kind of wire gauge can lead to ghastly consequences such as:
Using a wire size that can’t handle the current your motor generates can make the motor’s circuit breaker overheat quickly, causing the insulation to melt and the breaker to become useless.
Photo by Ksenia Chernaya
You’ll then have to rewire or even buy a new trolling motor and circuit breaker, which will no doubt cost a substantial sum of money. It’s better to avoid unnecessary expenses by using the correct wire size in the first place.
When you use the wrong size of wire for your trolling motor, it can prompt the circuits and electrical wires to heat up needlessly and spark an electrical fire in the middle of your float trip.
Not only is this kind of fire very difficult to put out, it can also take your trolling motor out of commission, cause serious damage to your boat, and lead to severe burns, or oven loss of human life.
Here are some important factors that you need to account for to help you decide which wire gauge is best for your trolling needs:
The amperage draw or requirements of your motor refers to the amount of power it pulls from your battery. Knowing the maximum amp draw of your trolling motor will enable you to figure out the size of wire and circuit breaker your system requires.
The higher the amp draw, the thicker the wire gauge you will need to use to ensure the wire can adequately handle the motor’s current.
Photo by Pixabay
To determine the amperage of your trolling motor, try examining the surface or consulting the motor’s manual. Most manufacturers print the max amp draw on the body of the motor.
If that doesn’t work, you can reach out to the manufacturer or merchant you purchased the device from or check out their website to get the information you want.
Alternatively, if you have a digital multimeter you can check your trolling motor’s amperage using the following steps:
- Turn on the amp settings on the digital multimeter and choose the appropriate range—it’s usually 10A or 20A.
- Start and run your trolling motor at maximum level.
- Connect the multimeter’s negative and positive leads to your motor.
- Take note of the reading displayed on the multimeter. That is your amp draw.
The farther away the motor is from the battery, the greater the length of wire that will be required. To ascertain what length of wire you should use, grab some measuring tape and calculate the distance from the trolling motor to the battery.
Photo by Ann H
Keep in mind that the wire gauge length varies based on the codes and standards used in making the wire. Make sure you account for these specificities before making final decisions on what length to use.
Voltage drop is the electric potential that dissipates along the path of currents passing through an electrical circuit.
As the wire length required for your trolling motor increases, you need to account for corresponding increases in voltage drop as a result of the wire’s resistance rising in response to the extended length.
Your trolling motor’s amperage will be impacted by high voltage drop. So when choosing wires, you will want to pick a size that’s thick enough to oppose the increased resistance and voltage drops that the extra wire length will cause.
The higher the length the thicker the wire or the lower the wire gauge rating you should opt for.
Your trolling motor’s maximum amperage will also influence the grade of wire you use. If your motor has a high amperage, a regular grade wire gauge will not be able to adequately handle the amperage.
For best results, you’ll be better off with a marine grade wire.
Ampacity or ampere capacity has to do with the current carrying capacity of a wire. It is the maximum amount of current a wire can carry continuously while being used without going beyond its temperature rating.
You have to choose the right wire size that can carry the current load of your trolling motor without overheating and damaging the equipment connected to it.
Photo by Tymur Khakimov
Luckily, there are plenty of ampacity charts out there that you can use to determine the correct wire gauge for your motor’s requirements without first having to do lengthy calculations.
They show the AWG size and diameter in both millimeters and inches, the resistance in ohms per 1000 feet and 1000 meters, and the cross-sectional area in mm2, inch2, and kcml.
The charts also display the current in amperes for different applications: power transfer and chassis wiring.
Not many people have the patience to carry out the complex calculations required to figure out the voltage drops for different wire lengths. This is where voltage drop calculators and tables come in handy.
There are numerous websites and services offering voltage drop calculators. Some examples include RapidTables, Calculator.net, and Electrical Technology. All you have to do is enter the wire type, size, length, and motor voltage and the expected voltage drop will be calculated and shown to you in seconds.
Photo by Paul Seling
Alternatively, you can use a voltage drop table like the one below to get results. This table’s calculations are based on a 3% voltage drop, AWG wire size, 105°C insulation rating, and 12-Volt motor systems.
To determine the recommended wire size for you from this table, check the horizontal axis to find your motor’s current load consumption and the vertical axis to find the wire length. Your correct AWG will lie at the intersection of the two variables.
Let’s take a look at the wire sizes that are commonly used for different trolling motor amperage ranges.
If you’re wondering what size of wire to use for your 12-volt trolling motor, the answer is that it depends on the motor’s amperage.
For a trolling motor with an amperage of 50 amps or thereabouts, an 8 gauge (8 AWG) wire will serve you just fine. However, if you’re using a 60 amps motor, you should go for the 6 gauge wire which is thicker and will be able to handle the extra current.
The recommended wire size to run for most 24-volt motor systems is 8 gauge. But if the length of wire you need is 20 feet or higher, it’s best to opt for a 6 gauge.
If you’re working with a 36-volt motor system, you can get away with fitting it with an 8 gauge or 6 gauge wire size. This should be enough to carry and transfer current without the heating going berserk and damaging your trolling system.
As explained earlier, the farther away the battery is from the motor, the longer the wire and the lower the wire gauge size you’ll need.
Photo by cottonbro studio
This is because wires with a low number or wire gauge ratings are bigger or thicker in size and therefore able to compensate for the increase in length and voltage drops.
Here are the appropriate wire sizes to use based on the distance from your trolling motor to the battery:
|Length (Feet)||20 Amp 12V Wire (240W)||30 Amp 12V Wire (360W)||40 Amp 12V Wire (480W)||50-60 Amp 12V Wire (600W-720W)|
|15 AWG||10 AWG||8 AWG||6 AWG||6 or 4 AWG|
|20 AWG||8 AWG||6 AWG||6 AWG||4 AWG|
|25 AWG||8 AWG||6 AWG||4 AWG||4 or 2 AWG|
|30 AWG||6 AWG||4 AWG||4 AWG||2 AWG|
|40 AWG||6 AWG||4 AWG||2 AWG||2 or 1 AWG|
|50 AWG||4 AWG||2 AWG||2 AWG||1 or 1/0 AWG|
|60 AWG||4 AWG||2 AWG||1 AWG||1/0 or 2/0 AWG|
|70 AWG||2 AWG||2 AWG||1/0 AWG||2/0 AWG|
|80 AWG||2 AWG||1 AWG||1/0 AWG||2/0 or 3/0 AWG|
|90 AWG||2 AWG||1/0 AWG||2/0 AWG||3/0 AWG|
Here are some tips you should apply when installing new wires on your trolling motor to ensure that everything worms as it should:
Photo by cottonbro studio
- Use proper wire routing methods to protect your motor against damage.
- Implement the correct connection methods and techniques to ensure secure and reliable transfer of current.
- Use of circuit breakers and fuses to maximize electrical safety.
- Test and verify the wiring setup before operating the trolling motor so you can identify and fix any issues before it has a chance to damage your whole system.
The size or AWG rating of the wire you choose for your trolling motor will depend primarily on the amperage of the motor and the length of the wire you require.
The more powerful your motor’s amperage is, the thicker the size and the lower the gauge wire rating you’ll need.
When you’re torn between two sizes, it’s better to go for a bigger wire than a smaller one that might end up not being strong enough to counter voltage drops and keep the circuit from overheating.
The importance of selecting a suitable wire size is integral to the smooth, safe, and efficient operation of your trolling motor. The wrong choice can easily damage your trolling system, warranting costly repairs or total replacements.
It’s always better to be safe than sorry so stick to the recommended guidelines as much as possible. If you’re ever in doubt or unsure of how to proceed, don’t hesitate to seek expert advice from your local electrician or hardware store manager.
Stay safe and happy boating!