Venerable trolling motor enters the electronics age, part 2
3/22/2021

Trolling motors are more popular than ever, and with competition among brands heating up, innovation and system integration have become the name of the game. In a recent issue of Marine Electronics Journal veteran marine writer Lenny Rudow gave us his take on the new crop and the advancements driving sales. Last week in part 1, Lenny talked about the importance of system integration and development of longer shafts, which permitted the use of trolling motors on larger boats. In this final segment, the focus is on power, specifically brushed vs brushless motors and more efficient batteries.

By Lenny Rudow

Motor matters


While modern trolling motors are pretty Space Age, they vary in how they carry out their primary function: moving the boat. In 1934, O.G. Schmidt built the first gear-driven electric trolling motor by strapping a prop to the starter motor from a Ford Model A and selling it under the name Minn Kota. Just as Schmidt’s company remains today, so does the technology he pioneered. Model A’s are a little more difficult to come by, but the motors Minn Kota currently uses are not as dissimilar as one might think. Brushed DC motors can be found in everything from power drills to golf carts, not to mention MotorGuide and Minn Kota trolling motors. However, Lowrance and Garmin both opted to use brushless DC (BLDC) motors in their new models. But, is brushless better?

The biggest advantage of brushed motors is their price. A 36-volt Ultrex with a 52-inch shaft is around $450 less expensive than a 50-inch Force. That being said, if you factor in optional extras they can be about neck and neck. BLDC motors, on the other hand, have three major benefits: efficiency, longevity and noise. Estimates vary wildly, but in general BLDC motors offer 5% to 40% greater efficiency, which means that more electricity is being converted into mechanical energy than into heat or noise.

All motors turn electricity into motion by generating moving electromagnetic fields—kind of like spinning a compass needle by moving a magnet around it. Brushed motors create fluctuating magnetic fields using carbon brushes. On the rotor (the part that spins) there are several little contact plates connected to copper coils. As the rotor rotates, the brushes make and break circuits with different contact plates, momentarily powering up alternating coils that create a magnetic field. As the name implies, BLDC motors don’t have brushes. Instead, they switch the magnets on or off using transistors controlled by a motor-driven circuit. Why does that matter? Brushes wear down as they rub against the contact plates, meaning that over time they become less effective until they eventually have to be replaced. While most people have never had to replace the brushes in their trolling motor, they may notice a drop in performance after many years of use. So theoretically, BLDC motors should offer better longevity. But since these motors are so new to the market, only time will tell for sure.

"Brushless motors offer quietness, efficiency and power,” says Lowrance EVP Lucas Steward. "No other trolling motor was using it at the time (that Ghost was developed). Brushless technology also eliminated sonar interference, a consistent problem we’ve dealt with for years. And a brushless motor is 40% more efficient. That’s a lot more fishing time regardless of the battery being used. Reducing battery weight and letting anglers run all day on a 24-volt system is a big deal.”

Garmin Media Relations Manager Carly Hysell agrees. "Brushless motors are the future of trolling motors and solve some of the power issues that have troubled customers in the past. Lithium battery technology will also evolve and make batteries more efficient.”


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