How to Size Trolling Motors to Boats

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Trolling motors are very popular additions to boats. Fishermen use them to slowly, and quietly, maneuver a boat into a favored spot without disturbing the fish. The typical trolling motor is mounted on the bow (front) of the boat and is controlled with a hand lever or foot pedal. Trolling motors are considered an add-on to most boats, so sizing one correctly takes diligence and a thorough evaluation of the environment in which you will be using it. Choosing the correct size for your boat will ensure smooth operations and plenty of power.

Determine the size and weight of your boat for maximum efficiency of the trolling motor. When a boat is manufactured, its weight and overall size is matched to the size of its main engine for cost-effectiveness, safety (as regulated by the Coast Guard) and efficiency. However, when it comes to trolling motors, a boater will often get the biggest one he can afford and give little thought to whether or not it is the right size for the boat it is mounted on.

Investigate the types of water typical for your boating. In heavier currents, found on rivers and in the ocean, your trolling motor must provide enough power -- also referred to as thrust -- to keep the boat on a steady course. Less thrust is needed in calmer waters, such as lakes and ponds. Wind is also a factor to consider, with more thrust needed in windier conditions.

Determine the weight limit on your boat. This information is required by the Coast Guard and is usually found stamped on a plate permanently affixed to the boat's interior. When calculating expected load, keep in mind persons and equipment you will regularly have on board. Trolling motors are heavy, and the added weight to the bow of your boat will affect handling and steering. Larger trolling motors require 24 volts of electricity for operation, and that will usually mean carrying an additional marine battery.

Research the various trolling motor manufacturers. Warranties vary across the industry, as does customer service. Size guidelines are available, but there are many variables in determining the correct size, so use them as a starting point only. It is often helpful to consult with a marine mechanic or reputable boat dealer to help with this decision, particularly if you are a novice boater.


  • Professional installation of your trolling motor is highly recommended.