Electric Outboard Speed and Range: Real-World Thames Numbers

What you can actually expect from an electric outboard on a river that never stops moving

Electric outboards look wonderfully simple on paper: quiet, clean, instant power, no petrol cans, no carburettor tantrums, and no pulling a cord like you’re trying to start a lawnmower from 1973. But when you put an electric outboard onto a real river with a real stream—yes, the Thames—Inevitably you want to know one thing:

How fast will it actually go, and how long will the battery really last?

Manufacturers love quoting perfect-laboratory numbers:
“Up to 8 hours of runtime!”
“Top speed 12 km/h!”

But on the Thames, where the stream can range from a gentle push to a full-on conveyor belt, the real-world figures look a little different.

Here’s a practical, honest guide to speed and range based on everyday Thames use with modern 3 kW–equivalent electric motors such as the ePropulsion and Torqueedo models found on Whaly boats and club safety craft.

1. The Thames Stream Factor

Before talking numbers, remember this:

Your speed over the water ≠ your speed over the ground.

If your motor propels you at 4.5 knots through the water:

With 1 knot of stream behind you, you’re suddenly doing 5.5 knots.
Against 1 knot of stream, you’re crawling along at 3.5 knots.
With 2 knots of flood, you’re practically flying.
Against 2 knots, you might wonder if your motor is switched on.

This dramatically affects the range because running against the stream demands much higher power.

2. Real-World Thames Speeds (Whaly with ePropulsion 3 kW)

Approximate speeds with one or two adults aboard:

Power Setting	Speed Through Water	Speed Over Ground (1-knot stream)
300 W (slow)	~2.5 knots	With stream: 3.5 knots / Against: 1.5 knots
600 W (cruising)	~3.5 knots	With: 4.5 / Against: 2.5
1200 W (fast cruise)	~4.5 knots	With: 5.5 / Against: 3.5
2500–3000 W (full power)	~5–6.5 knots	With: 8–9 / Against: 4–4.5

In practice, the boat feels happiest around 600–1200 W, where noise is low, power is stable, and the battery efficiency is fantastic.

3. What About Range? Real Battery Life Numbers

Using a 30 kg ePropulsion battery (approx. 3 kWh usable capacity):

Light Use / Filming / Safety Boat Standby (300–400 W)

Typical for escorting dinghies or filming slow manoeuvres
Range: 9–12 hours
Perfect for club days, training sessions or exploring.

Steady Upstream Cruising (600–800 W)

Going against moderate stream
Range: 3–4.5 hours

Fast Cruise (1200–1500 W)

Useful when you need to get somewhere quickly
Range: ~2.5–3.5 hours

Full Power Burst (2500–3000 W)

For emergencies, strong stream, or retrieving a dinghy rapidly
Range: 60–90 minutes max

Electric motors are extremely efficient, but doubling the speed roughly quadruples the energy consumption. The Thames is the perfect playground for learning this quickly.

4. A Practical Estimate for a Typical UTSC Session

A standard safety boat morning at the club might look like this:

Slow cruising while observing: 300–500 W
Occasional upstream repositioning: 800–1500 W
One or two short emergencies: 2000 W+

Across a 3–4 hour session, most crews use 20–40% of the big ePropulsion battery.

You’ll almost never run out unless you insist on doing the whole session at full throttle (which the Whaly finds deeply undignified anyway).

5. Tips for Maximising Range

Electric outboards reward good habits:

✔ Cruise below 1000 W

This is the sweet spot for efficiency.

✔ Avoid prolonged upstream full-power runs

Use the slacker-water channels close to the bank where the stream is weaker.

✔ Trim the boat properly

More level boat = less drag = more speed for the same wattage.

✔ Check your prop

A weed-wrapped propeller makes even the fanciest outboard feel like a hand whisk.

✔ Use momentum

Let the boat glide when you can. Electric motors excel at quick on/off adjustments.

6. Why Electric Still Wins

Despite the limitations, electric outboards are superb for the Thames:

Quiet—no one hears you coming except the swans
No fumes in your face all morning
Instant torque for fast acceleration
Much safer for teaching and filming
Low running cost
Solar charging at home (the true Thames sailor’s superpower)

Once you’ve used electric for a while, going back to petrol feels… medieval.

Final Thoughts

Electric outboards are transforming how we move up and down the Thames. While the marketing numbers are optimistic, the real-world figures on Whaly boats show they’re more than capable of safety duties, filming work and general river cruising—provided you understand the relationship between power, speed and stream.

Use moderate power, glide when you can, and the battery will last far longer than you expect. And enjoy the silence—your dinghy sailors certainly will.

pmr sailing

Monday, 8 December 2025