How To Choose Trolling Motor Thrust

Thrust is the only number that matters when you first size a trolling motor, and it is the number buyers most often get wrong. Hull length is a proxy; the real driver is the loaded weight of the boat and the water it works in.

Start With Loaded Weight Not Hull Length

A 3 m tender with one angler and a light battery behaves nothing like the same hull with two adults, a cool box and a 100AH lead acid battery. Add up hull, battery, crew and gear, then read against the published maximum boat load for each series.

Published factory figures. The DT, ET and FT Series sheets list thrust, current and output but not a boat load rating; use the P Series figures as a reference point and confirm with sales.

Add Margin For Wind Current And Salt

The maximum figures above assume reasonable conditions. If the boat works exposed water, tidal current or an onshore breeze, size one step up. A motor held near its maximum current all day draws more from the battery and runs hotter than the same motor working at half throttle.

Then Check Current Draw Against Your Battery

Two motors with the same thrust can draw very different current. The brush series is rated at 11A with a maximum that matches the thrust figure, so a 65 lbs unit peaks at 65A. The brushless series is rated at 5A, with maximums of 40A to 80A depending on model. Read the specification table before you specify cable and fusing.

A Quick Working Method

1. Add up loaded weight including battery, crew and gear
2. Find the series whose maximum boat load is above that figure
3. Add one step if the water is exposed, tidal or salt
4. Check the maximum current against the battery and cable you can fit
5. Confirm the transom will take the shaft length, 609 mm or 788 mm

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