top of page

Black Box Techniques

Chapter V. Tips on Adjusting the Black Box


  1. If you are not catching fish, the natural inclination is to turn the Black Box up to a higher voltage. Often this is the wrong way. Most of the time you want to reduce the natural electrolysis voltage for best results. Sometimes you can tell if you have the Black Box voltage too high by watching hooked fish as you reel them near the boat. If your voltage is too high, they will fight violently and will try to swim under the boat and into the prop wash where the voltage is lower.

  2. Larger fish need less voltage than smaller fish. Their large body size makes them more sensitive to the electric charge. For very large fish (over 20 or 30 pounds) you may want to turn the voltage down about .1 volt. You should also lower the voltage for extra sensitive fish like sharks. Note: As you dial the Black Box, it will show readings down to zero.

  3. As you are searching for the best voltage, make very small adjustments. Often, a small change is all that is needed to attract the fish you are after.

  4. If you are running more than one downrigger, it is best to hook all of them to the Black Box to avoid having different voltages on each downrigger. By connecting all of the downriggers together, it creates a uniform positive charge around the entire hull which is highly desirable. The Black Box has the power to run up to six downriggers.


A number of questions arise on how to adjust the Black Box as you fish deeper. There is less loss than you might suspect as you go 50, 100 or even 200 feet down. Each section of downrigger cable is reacting separately with the boat's hull and its zinc, thereby creating its own natural voltage through the process of electrolysis. Using insulated wire, we have measured this voltage as deep as 400 feet and found very little change in the charge generated. The Black Box is adjusting and controlling your rate of natural electrolysis to the setting you desire. This will carry right down the wire in both fresh and saltwater.















Zinc annodes are installed on outdrives or motor shafts to protect from electrolytic corrosion. Note the heavily corroded condition of this zinc. When the zinc is more than 50% corroded, it should be replaced.

bottom of page