Thrust and speed are not the same thing. A trolling motor’s thrust rating tells you about its pushing force; it doesn't promise a particular top speed. The boat’s fully loaded weight is the starting point for a useful comparison.
Start with loaded weight
Minn Kota's published rule of thumb is at least 2 pounds of thrust for every 100 pounds of fully loaded boat weight. That weight includes people, gear, fuel and batteries—not merely an empty hull or a brochure's dry weight.
Keep a note of whether you regularly fish in high wind or current, and check what voltage system your candidate motor requires.
Why the calculation is only the beginning
Two similarly heavy boats can handle differently. Hull shape, windage, the height of a pontoon's side panels, current, and your intended use all affect how much control you need. A motor that is comfortable for sheltered lakes may struggle holding position in wind and chop.
The best purchase may be a more capable system than a simple minimum-weight calculation suggests. Compare real motor specifications, compatible batteries, available shaft lengths and your boat's wiring before choosing.
What about 12V, 24V and 36V?
Trolling motors are offered in different voltage systems, and the voltage influences the battery and wiring setup. Do not assume you can simply connect any battery to any motor. Buy the components as a compatible system, following the manufacturer's instructions and appropriate overcurrent protection requirements.
Estimate the full loaded boat weight → check baseline thrust → consider wind/current → verify shaft length → match motor voltage to batteries and wiring → compare specific motors.