Trolling Motor Wire Size Calculator
Find the exact wire gauge for your trolling motor setup. This tool automatically accounts for continuous-load safety factors and enclosed conduit thermal derating.
Approx: 55 lb thrust ≈ 50A, 80 lb thrust ≈ 60A.
Distance from battery to motor. (Tool automatically doubles this for round trip).
Check this if wires run inside a tube or packed conduit where heat cannot escape easily. Applies a 20% thermal derating (requires next larger wire size).
Why trolling motors need accurate wire sizing
Trolling motors draw heavy, continuous current (frequently 50 amps or more) to push your boat through water and wind. Because the batteries are usually installed at the stern and the motor at the bow, the electrical run can easily exceed 20 feet. This long distance paired with high continuous current makes trolling motor circuits incredibly vulnerable to voltage drop. If the wires are too thin, voltage drops before reaching the motor, causing a loss of thrust and dangerous overheating in the wiring.
Free-Air vs. Enclosed Conduit Derating
Electrical wire naturally heats up as current flows through it. When wires are run in "free air" (open spaces where air can circulate), this heat dissipates safely. However, if you pull your trolling motor wires through an enclosed PVC pipe, flexible conduit, or a tightly packed wiring chase, that heat gets trapped.
To prevent the insulation from melting in these enclosed spaces, marine electrical standards require a thermal derating—typically reducing the wire's effective ampacity by 20%. In practice, this means if you are running wire through a conduit, you must usually step up to the next thicker wire size.
Trolling Motor Wire Size Reference Chart
Below is a quick reference table for common trolling motor setups. These recommendations assume a 3% maximum voltage drop and include a 1.25x safety margin. Always use the interactive calculator above for your specific run length.
| System Voltage | Approx. Thrust / Amps | Short Run (10 ft) | Medium Run (20 ft) | Long Run (30 ft) |
|---|---|---|---|---|
| 12V | 55 lb / 50A | 6 AWG | 4 AWG | 2 AWG |
| 24V | 80 lb / 60A | 8 AWG | 6 AWG | 4 AWG |
| 36V | 112 lb / 50A | 10 AWG | 8 AWG | 6 AWG |
| 48V | 130 lb / 40A | 10 AWG | 10 AWG | 8 AWG |
* Note: Distances are one-way (battery to motor). Recommendations assume standard 75°C marine copper wire in free air.
Frequently Asked Questions
For a typical 24V trolling motor drawing 60 amps, you generally need 8 AWG wire for short runs under 15 feet, and 6 AWG wire for runs between 15 and 25 feet. If your wiring is in an enclosed conduit, always upsize to the next gauge.
You can run trolling motor wire as far as necessary, provided you increase the wire thickness (lower AWG number) to compensate for the distance. If you need to run wire 30 feet to the bow, a 12V system might require massive 2 AWG cable, whereas a 36V system could make the same run with much cheaper 6 AWG wire.
Yes, critically. Undersized wire will cause a significant voltage drop, meaning your expensive 24V motor might only receive 20V by the time the power reaches the bow. This results in sluggish performance, reduced thrust, and dangerous heat buildup in the wires that can start a fire.
Methodology: The Math Behind the Calculator
This calculator determines the safe wire size using two parallel checks:
- Voltage Drop (Circular Mils): Uses the standard DC formula
CM = (2 × 10.75 × L × I) ÷ V_dropto ensure the voltage drop does not exceed your target (usually 3%). Because trolling motors lack a chassis ground, the total circuit length is doubled (2 × L) for the round trip. - Thermal Ampacity: Trolling motors are considered continuous loads, so the input amperage is multiplied by a 1.25 safety factor. We then check the resulting "Design Current" against standard 75°C copper ampacity tables.
Finally, if "Enclosed Conduit" is selected, the tool automatically steps up to the next larger AWG size to account for the trapped heat and 20% thermal derating rule.