How Much Thrust Do You Really Need? A Boater's Guide

A Question Older Than Motors

Long before electric trolling motors existed, boat builders wrestled with a question that sounds modern but is ancient: how much force does it take to move this boat through this water?

The 19th-century naval architects who designed clipper ships calculated displacement, drag, and sail area by hand, in ledgers, with formulas derived from centuries of trial and error. The steam engineers of the 1880s rated their paddle-wheel boats in indicated horsepower — a measure of the work done inside the cylinder — because they had no clean way to measure the actual push delivered to the water.

When Ole Evinrude built his first outboard in 1909, he rated it in horsepower — borrowing the unit James Watt had devised in the 1780s to sell steam engines to mine owners by comparing them to the draft horses they replaced. Horsepower stuck. To this day, gas outboards are sold in HP: 2.5, 9.9, 50, 150.

But when the modern electric trolling motor emerged in the 1930s, the industry adopted a different unit: pounds of thrust. This wasn't arbitrary. Horsepower measures power (energy over time); thrust measures force (the actual push). For a slow-moving trolling motor — where speed isn't the goal and the propeller is optimized for low-RPM grunt rather than high-RPM speed — thrust is the more honest metric. It tells you what the motor can actually do against wind and current, which is what matters when you're trying to hold a boat in place.

The problem is that "pounds of thrust" is a number most boaters find mystifying. A 55-lb thrust motor — is that enough? Too much? For what boat? The unit doesn't intuitively map to "my 16-foot boat with three people in it."

This guide exists to fix that. By the end, you'll know exactly how much thrust you need — and why.

The Rule of Thumb

Here's the formula that serious anglers use, refined over decades of trial on American and Canadian lakes:

Boat weight (in pounds, fully loaded) ÷ 100 × 2 = minimum thrust (in lbs)

Or, more simply: 2 lbs of thrust for every 100 lbs of boat, passengers, gear, and motor.

Let's break that down with an example. Say you have a 16-foot aluminum fishing boat. Here's the math:

Component	Weight
Boat (16 ft aluminum)	600 lbs
Motor + battery + fuel	150 lbs
2 passengers	350 lbs
Gear, cooler, tackle	100 lbs
Total	1,200 lbs

Applying the rule: 1,200 ÷ 100 × 2 = 24 lbs minimum thrust.

But that's the minimum — the thrust required to move the boat at all in calm water. It doesn't account for wind, current, or the need to hold position against environmental forces. For real-world use, you want a buffer, and you want to account for the worst conditions you'll fish in.

The practical guidance most experts use:

Total Loaded Boat Weight	Recommended Thrust
Under 1,500 lbs (small boats, kayaks, 12–14 ft)	30–45 lbs
1,500–2,500 lbs (14–16 ft fishing boats, 2 people)	45–55 lbs
2,500–3,500 lbs (16–18 ft, 2–3 people)	55–70 lbs
3,500–5,000 lbs (18–20 ft, 3+ people)	70–100 lbs
5,000+ lbs (large bass boats, pontoons)	100–112+ lbs

Why "More Is Better" Is a Trap

It's tempting, when you see a 55-lb and an 80-lb motor at similar prices, to buy the 80. More thrust is more better, right?

Not always. Here's why over-sizing your motor has real costs:

1. Battery Drain

A motor draws current roughly proportional to the thrust it's producing. An 80-lb thrust motor running at full power draws significantly more amps than a 55-lb motor at full power. If your battery is sized for a 55-lb motor, an 80-lb motor will drain it faster — leaving you with less runtime, not more.

2. Weight and Clutter

Bigger thrust generally means a bigger motor — heavier shaft, larger head, heavier mounting bracket. On a small boat, that's weight you carry every time you load and unload, and bulk that clutters the bow.

3. Voltage System Implications

Thrust and voltage are linked. A 55-lb motor can run on 12V. A 70+ lb motor typically needs 24V (two batteries in series). An 80+ lb motor often needs 36V (three batteries). So buying more thrust may force you into a higher-voltage system — meaning more batteries, more cost, more weight. (We cover voltage systems in detail in our next article.)

4. Diminishing Returns on a Small Boat

On a 1,500-lb boat, the difference between 45 lbs and 55 lbs of thrust is meaningful. The difference between 70 lbs and 100 lbs is wasted — you'll never use the extra thrust, and the motor will spend most of its life running at 30% power, where it's less efficient than a smaller motor running at 50%.

The Variables Most Boaters Forget

The rule of thumb gets you close. But real-world thrust needs depend on variables that aren't in the formula. Here are the four most commonly underestimated:

Wind

Wind is the single biggest factor in trolling motor sizing, and the most underestimated. A 15 mph wind on a 16-foot boat generates significant lateral force — the boat acts like a sail. Holding position against that wind requires thrust well beyond what's needed to move the boat in calm conditions.

Rule: if you regularly fish in winds over 10 mph, add 10–20 lbs to your calculated thrust.

Current

River anglers and tidal-water anglers face constant current. A motor that holds a boat in a 2 mph current is working harder than the same motor holding a boat on a still lake. If you fish moving water, size up.

Boat Profile

A low-profile bass boat catches less wind than a high-sided pontoon or a deep-V walleye boat. The "sail area" of your boat matters. Pontoon owners in particular often find they need more thrust than the formula suggests, because their boat acts like a billboard in any breeze.

Usage Pattern

Are you using the motor to creep along a shoreline at 0.5 mph, or to run across a bay at 3 mph? The first task needs little thrust. The second needs sustained higher output. Match your motor to how you'll actually use it.

The Kayak and Canoe Exception

The formula and the table above assume traditional boats. For kayaks, canoes, and paddleboards — which weigh a fraction of what a fishing boat does — the math is different.

Craft	Typical Loaded Weight	Recommended Thrust
Fishing kayak (12–14 ft, 1 person + gear)	300–450 lbs	30–45 lbs
Canoe (16 ft, 2 people + gear)	500–700 lbs	30–45 lbs
SUP with fishing gear	250–350 lbs	30 lbs
Small pontoon (one-person)	400–600 lbs	30–45 lbs

For these craft, 30–45 lbs of thrust is almost always sufficient. The bigger consideration isn't thrust but weight and mounting — you want a motor light enough not to unbalance a kayak, and a mounting system that works on a vessel without a transom. (We cover this in our article on kayaks going electric.)

A Quick Self-Check

Before you buy, answer these five questions:

What's my fully loaded boat weight? (Boat + motor + battery + people + gear. Be honest — most people underestimate by 20%.)

What's the windiest condition I'll fish in? (Add thrust for wind.)

Do I fish current? (Add thrust for current.)

What's my boat's wind profile? (Pontoon? Deep-V? Add thrust.)

What voltage system am I willing to run? (12V caps out around 55 lbs. More thrust means 24V or 36V.)

The intersection of those answers will tell you whether you need a 45-lb 12V motor, a 70-lb 24V motor, or something larger. And it'll prevent the two most common mistakes: buying too little and being stranded on a windy day, or buying too much and carrying the cost and weight of thrust you'll never use.

Where BateriaPower Comes In

At BateriaPower, we're developing a range of bow-mounted electric thrusters engineered to cover the real-world thrust needs of anglers and families across the US, Europe, and Canada — without forcing you into an oversized, overpriced system.

We're building motors sized for the boats people actually own — the 45–55 lb range for the 14–16 foot fishing boat that's the most common hull on American and Canadian lakes, and the 55–80 lb range for the larger rigs that need more. And we're building each motor to deliver its rated thrust honestly — not a peak number that lasts 30 seconds, but sustained thrust you can count on for a full day on the water.

We believe sizing a motor shouldn't require an engineering degree. Our goal is to make the choice simple: tell us your boat, tell us your water, and we'll tell you the right motor — at a price that respects your budget.

Join the BateriaPower waitlist to follow our development of electric thrusters sized for real boats — and be among the first to know when they're ready.