There are several reasons why it might be useful to know the amperage that your trolling motor draws while you’re using it. However, getting this number might be harder than you think.
If you want to find the amperage of your trolling motor, here’s what you need to know. Once you understand these things, you should be able to get the numbers you need to make the calculations you’ve been trying to make.
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Why Do I Want to Know My Amp Draw?
There are several reasons why you might want to know the amperage draw of your trolling motor. These may not all apply to you but you might be surprised at how useful this number can be.
First of all, knowing the actual amperage that your trolling motor draws can allow you to make sure that it is working well. Compare this to the amperage that the manufacturer gives you to determine whether or not your motor is working as it should.
Knowing this number can also be useful if you need to take your trolling motor in for repairs. If you know the amperage draw is not what it should be, this can help a mechanic know which repairs need to be made, or at least what tests to run.
Knowing your amp draw will also allow you to accurately calculate how long your trolling motor should run off its battery. Simply divide the amperage drawn by the amp hours that your battery is rated for.
For instance, if your battery is rated for 100 amperage hours and your trolling motor is drawing 25 amps, divide 100 by 25 to get 4. Your trolling motor battery should last for 4 hours.
You can calculate the number of amps drawn if you have the number of watts the motor is using. Just divide the number of watts drawn by the voltage that is powering the system.
For example, if your system is pulling 300 watts and you have a 12-volt trolling motor, divide 300 by 12 to get 25. This is the amperage that the motor is currently pulling. You can use this to further calculate how long your trolling motor should last, as outlined above.
Consult the Manufacturer
The easiest way to get the amperage that your trolling motor draws is to look in the manual. You can also search the make and model of the trolling motor online, along with the word “amperage”, to get this number.
However, many companies only show the maximum amperage that their trolling motors draw. This number is usually the amperage at the speed highest setting.
If you don’t run your motor at the highest setting all the time, or you only use that setting some of the time, calculations based on this number may be inaccurate. However, the numbers you get from these calculations would be your worst-case scenario.
If, for instance, you calculate how long your trolling motor will last based on this amperage, then you know the minimum amount of time that it should run. You can also know that you could conserve power and make it last longer by running the boat at lower speeds.
Note that this number is only useful to you if your trolling motor is working well. If it’s having electrical issues, it may not be drawing as many amps as it should be. In these cases, you will want to try to find the actual amperage rather than the ideal or tested amperage.
Use an Amp Meter
If you want to test the amperage on your trolling motor yourself, you’ll need to buy a voltage/amperage meter. The easiest kind to use will plug into your trolling motor on one side and your battery on the other.
However, you can also use one with contact leads. You will just have to be more “hands-on” during the test with this meter than you would have to be with one that plugs in.
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Attach the plugs to your meter or touch the negative contact lead to the negative side of your battery and the positive lead to the positive side. Start running your trolling motor at its lowest speed.
Keep an eye on your meter while you do this. You’ll want to make sure you know the amperage that the motor is drawing while it is getting up to speed as well as the amperage it draws when it is at full speed.
If you want to note these numbers down, do so. This can be a good way to test your trolling motor every once in a while to make sure it is still functioning optimally. If these numbers change, it may need a tuneup or a repair.
Change speeds on your trolling motor and follow this procedure at each speed setting. Again, make sure you note the amperage it is drawing while it gets up to speed and once it is going full speed.
You may need to take an average for these numbers because the amperage draw can fluctuate second by second. Watch your meter to find out how often this changes for your boat and your trolling motor.
Some people choose to keep their pluggable amp meter connected all the time, but this isn’t necessary. Checking these numbers now and then will give you a good idea of how well your boat is working.
This video shows you how to use an amp meter to calculate your trolling motor’s amperage draw.
Finding the amperage draw of your trolling motor can be a challenge, but you don’t need to worry. Following the instructions outlined above, you should be able to find the numbers you need or to calculate them so you can use them as you need to.
Learning to find the amp draw of your trolling motor can be fun and it could help you, too. Become a more informed angler today when you learn more about how the electricity of your trolling motor works.