Some articles and people on the internet say to use a 50Amp circuit breaker, and you will be fine.
However, that’s not how it works. You have to know why that is for your safety and the safety of others.
To determine the appropriate fuse size for a trolling motor, follow these steps:
- Check the trolling motor’s specifications: Locate the maximum current draw (in amps) in the owner’s manual or the manufacturer’s website. This information is crucial in determining the correct fuse size.
- Apply the 125% safety factor rule: Multiply the maximum current draw by 1.25 (125%). This will ensure the fuse is slightly larger than the motor’s maximum current draw, providing an adequate safety margin.
Example of a Calculation
If the trolling motor has a maximum current draw of 40 amps, multiply 40 by 1.25
40A*1.25= 50A
In this case, a 50-amp fuse would be appropriate. I highly recommend Bluesea Systems for fuses. You will pay a little bit more than no-name brands, but it’s well worth it in my opinion. Check them out here.
If we have a Minn Kota power drive trolling motor, it will draw a maximum of 50Amps. This is how we will size a circuit breaker for this trolling motor:
50A*1.25= 62.5A
We need a circuit breaker that is higher than 62.5A. The next closest circuit breaker is 70A (link). We need to ensure that the wire can handle a larger current draw. Which is what we will discuss next:
Current of the circuit breaker needs to be lower than the current of the wire
Remember that the primary purpose of a fuse is to protect the electrical wiring and equipment from potential damage caused by excessive current. This means that the current of your fuse needs to be smaller than the rated current of the wire. In another article, I explained how to select a wire size for a trolling motor.
In that article, we have selected a wire which complies with several factors, including:
- Current
- Voltage
- Voltage drop
A 6AWG wire can handle a current of 75A at a 90°C insulation rating (resources). Using a 50A circuit breaker is safe because it will trip first before the wire melts.
Conclusion
This is how you calculate the fuse size for a trolling motor.
If you have questions, feel free to leave them below or send me an email.
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I’m an off-grid enthusiast. I created this website to give clear and straight-to-the-point advice about solar power. I’m also the author of the book ‘Off-grid solar power simplified‘. Read more about me on my about page, check out my Youtube channel, or send me a message.