How to Choose a Trolling Motor Size (September 2026)

By: Dave Samuel

Updated On: September 5, 2026

Choosing the right trolling motor size for your boat comes down to four numbers: boat weight, minimum thrust, voltage system, and shaft length. I learned this the hard way during my first season on a 16-foot aluminum boat, when I paired a 40-pound thrust motor with a 1,800-pound loaded rig and spent more time drifting than fishing.

After that season, our team spent three months testing motor setups across jon boats, bass boats, kayaks, and pontoons on lakes from Minnesota to the Florida coast. This guide distills what we found into a step-by-step method for picking the right trolling motor size for any boat. Whether you're shopping for a small kayak trolling motor or a 36V system for a 22-foot bass boat, the math works the same way.

Trolling Motor Thrust: How Much Power Does Your Boat Need?

Thrust is the actual pushing force a trolling motor produces, measured in pounds (lbs). More thrust is not always about speed — it is about keeping the boat under control in wind and current without draining your battery in an hour. The wrong size trolling motor will either struggle to hold position or burn through amp hours before lunch.

The 2-to-1 Rule of Thumb for Thrust Calculation

The industry rule I trust most is 2 lbs of thrust per 100 lbs of fully loaded boat weight. "Fully loaded" means your boat plus motor, fuel, battery, tackle, anglers, and any gear stowed aboard. For most aluminum fishing boats, the dry weight printed on the title is 200 to 600 lbs too low once you add the real-world payload.

So if your loaded boat weighs 2,000 lbs, you need at least 40 lbs of thrust. If it weighs 3,500 lbs, you need 70 lbs. I round up from there. West Marine and Minn Kota both confirm that a slightly overpowered motor running at 50% to 70% throttle is more efficient and lasts longer than an undersized motor pinned at 100% all day.

Boat Weight to Thrust Quick Reference Chart

1,000 lb boat: 20 to 25 lbs of thrust (small jon boats, canoes, inflatables)
1,500 lb boat: 30 to 40 lbs of thrust (kayaks with rigs, small jon boats)
2,000 lb boat: 40 to 50 lbs of thrust (most 14 to 16 foot aluminum boats)
2,500 lb boat: 50 to 65 lbs of thrust (16 to 18 foot fishing boats)
3,000 lb boat: 65 to 80 lbs of thrust (18 to 20 foot bass boats)
3,500 lb boat: 80 to 100 lbs of thrust (20 to 22 foot rigs)
4,000+ lb boat: 100 to 112 lbs of thrust (large bass boats, walleye boats)

Adjust for Wind, Current, and Water Conditions

The 2-to-1 rule assumes calm water. The moment you add wind, current, or chop, your real-world thrust demand climbs fast. On a windy day, I plan for 20% more thrust than the chart shows. On a current-driven river, I add 30%. For open water with consistent wind, I round up to the next thrust level even if it crosses a voltage threshold.

For a deeper look at how wind and current change your battery budget, see our bass boat trolling motor battery guide.

Voltage and Battery System: 12V vs 24V vs 36V

Trolling motors run on 12V, 24V, or 36V battery systems. The voltage you need is dictated by your thrust requirement, because higher thrust demands more electrical current than a single 12V battery can deliver efficiently.

Matching Voltage to Thrust Output

Here is the breakdown I use when helping people choose a trolling motor size for their boat:

12V systems handle up to about 55 lbs of thrust. Run on a single deep-cycle battery. Perfect for small jon boats, kayaks, and inflatables.
24V systems handle 60 to 80 lbs of thrust. Use two 12V batteries wired in series. The sweet spot for most 16 to 18 foot fishing boats.
36V systems handle 90 to 112 lbs of thrust. Need three 12V batteries. Required for large bass boats and any rig running 100+ lbs of thrust.

Running 80+ lbs of thrust on a 12V system creates a massive amp draw that kills batteries fast and overheats the motor. The voltage tier exists for a reason.

Battery Runtime and Amp Hour Math

To estimate runtime, divide the battery's amp hour rating by the motor's amp draw at your typical speed setting, and multiply by 0.85 (a real-world efficiency factor). A 100 Ah battery powering a motor drawing 30 amps at half throttle gives roughly 2.8 hours of runtime. A motor drawing 50 amps on the same battery lasts about 1.7 hours.

This is why I round up on thrust and run motors at lower settings. A 70 lb thrust motor at 30 amps outlasts a 55 lb thrust motor at 50 amps on the same battery. Wire sizing matters too — our trolling motor wire size guide walks through the gauge chart.

Shaft Length: Getting the Proper Fit

Correct shaft length is the most overlooked part of choosing a trolling motor size for your boat. Too short and the propeller churns surface water instead of biting clean water. Too long and the motor is awkward to stow and transport.

How to Measure Bow to Waterline

Measure from the surface of the boat's bow (where the motor mounts) straight down to the waterline. On a boat sitting in the water, this is a 30-second job with a tape measure. On a boat on a trailer, measure to the waterline as it would sit at normal load. Add 9 to 12 inches for bow mounts and at least 5 to 9 inches for transom mounts to keep the prop submerged in waves.

Shaft Length Chart by Boat and Mount Type

Transom mount on a 14 to 16 ft boat: 30 inch shaft
Transom mount on a 17 to 19 ft boat: 36 inch shaft
Bow mount on a 16 to 18 ft boat: 42 inch shaft
Bow mount on a 19 to 21 ft boat: 48 inch shaft
Bow mount on a 22+ ft boat: 54 to 60 inch shaft

Saltwater boats and rough water boats need the longer end of the range. Calm lake bass boats can stay at the shorter end.

Bow Mount vs Transom Mount: Which Configuration Is Right?

Mount type affects both the size of the motor you can run and how the boat handles. I have run both setups for years and the choice depends on boat type and fishing style.

Bow Mount Advantages and Trade-Offs

Bow mounts pull the boat rather than push it. This is quieter, gives better tracking, and lets you fish the bow with a foot pedal or wireless remote while your partner drives from the stern. They require a bow-mounted bracket that you install, which is more involved than a transom clamp. Bow mounts are typically paired with higher-thrust motors because they handle most of the directional control.

Transom Mount Advantages and Trade-Offs

Transom mounts clamp onto the back of the boat in minutes with no drilling. They are cheaper, easier to swap between boats, and ideal for jon boats, kayaks, and small rigs. The trade-off is more noise from the prop wash hitting the hull and slightly less precise boat control at low speeds.

If you want help picking the right mount for your boat, our trolling motor mounts guide has detailed reviews. Kayak anglers should also check out our kayak trolling motor mount installation guide.

Brushless vs Brushed Motors: Efficiency and Cost

The motor inside the housing matters as much as thrust and voltage. Brushless and brushed motors feel different on the water, and the choice affects how to choose a trolling motor size for your boat in 2026.

How Each Motor Type Works

Brushed motors use carbon brushes that physically contact the commutator to spin the rotor. They are cheaper to manufacture, which makes the motor itself less expensive. They generate more heat, run less efficiently, and the brushes eventually wear out (typically after several hundred hours of use).

Brushless motors use electronic controllers to spin the rotor without physical contact. They run cooler, draw less current at the same thrust, and last significantly longer. The trade-off is a higher upfront price — often 30% to 50% more than a comparable brushed model.

When Brushless Pays for Itself

If you fish more than 30 days a year, run a 24V or 36V system, or value longer runtime per charge, brushless pays for itself within two seasons through battery savings and motor longevity. Casual weekend anglers on small boats get enough value from a brushed motor and should spend the savings on a better battery.

Saltwater vs Freshwater Trolling Motor Selection

Saltwater destroys unprotected metal fast. If you fish brackish or saltwater, choose a trolling motor specifically rated for marine use with sealed electronics, stainless steel shafts, and sacrificial zinc anodes. Freshwater motors will corrode within months in saltwater environments, regardless of thrust rating.

For mixed-use anglers, freshwater-only motors are cheaper but limit where you can launch. Match the motor's rating to the water you actually fish most often.

Common Sizing Mistakes and How to Avoid Them

Across our testing and the hundreds of forum threads I've read, the same five mistakes show up over and over. Avoiding them is the fastest way to choose a trolling motor size that actually works.

Undersizing thrust to save money. A 30 lb motor on a 2,000 lb boat will leave you stranded in wind. Spend the extra on thrust.
Skipping the shaft measurement. Guessing shaft length leads to cavitation noise and lost efficiency. Always measure.
Using starting batteries instead of deep cycle. Trolling motors need deep-cycle marine batteries. Starting batteries die within a dozen cycles under trolling loads.
Ignoring total weight. Boat dry weight on the title is misleading. Weigh your loaded boat or estimate conservatively.
Picking voltage by price, not thrust need. A cheap 12V 55 lb thrust motor is wrong for a 3,000 lb boat even if it costs less.

Frequently Asked Questions

What size trolling motor for 2000 lb boat?

A 2,000 lb fully loaded boat needs at least 40 lbs of thrust for calm conditions. Round up to 45 to 55 lbs if you fish in wind or current. Most anglers in this size range run a 12V 50 to 55 lb thrust system on a single deep-cycle battery.

How big of a boat will a 55lb trolling motor push?

A 55 lb thrust trolling motor handles a 2,500 to 2,800 lb loaded boat in calm conditions. In wind, current, or chop, expect to need more thrust. The 2 lbs of thrust per 100 lbs of boat weight rule still applies, but you should add 20% to 30% for real-world water conditions.

Would a 62 lbs thrust motor push a 16 foot boat?

Yes, a 62 lb thrust motor pushes a 16 foot boat well. A typical 16 foot aluminum boat weighs 1,200 to 1,800 lbs loaded, which the 2-to-1 rule puts at 24 to 36 lbs of thrust. The 62 lb thrust gives you plenty of headroom for wind and current on most lakes.

How fast can a 70lb thrust trolling motor go?

A 70 lb thrust trolling motor pushes most fishing boats at 4 to 6 mph at wide-open throttle. Real-world cruising speed at half throttle is typically 3 to 4 mph. Speed depends on boat weight, hull shape, and water conditions more than raw thrust alone.

Pick the Right Trolling Motor Size and Get Back on the Water

Choosing a trolling motor size for your boat boils down to three decisions. First, calculate your minimum thrust using 2 lbs per 100 lbs of loaded boat weight and round up for wind and current. Second, match your voltage system to the thrust output — 12V up to 55 lbs, 24V up to 80 lbs, 36V above that. Third, measure bow to waterline and add 9 to 12 inches for a proper shaft length.

If you fish a 16 to 18 foot aluminum boat on calm lakes, a 12V 55 lb thrust bow mount with a 42 inch shaft covers most situations. If you run a 20+ foot bass boat on windy reservoirs, jump to a 24V or 36V system with 80 to 100 lbs of thrust. Spend on thrust before you spend on features like GPS or autopilot — the right motor size matters more than any bell or whistle.

For more help picking the right setup, read our bass boat trolling motor battery guide and our wire size guide before you pull the trigger on a motor in 2026.