Electric boat motor range: how far can you go on one charge? Torqeedo, ePropulsion and Aquamot

On one charge you can travel anywhere between 7 and 171 km, depending on motor, battery and speed. The biggest factor is not the battery but your speed: at slow speed the same motor with the same battery usually covers two to four times the distance it manages at full throttle, and at walking pace more than ten times. That is what the range tables from Torqeedo, ePropulsion and Aquamot show.

What determines the range of an electric boat motor?

Range depends mainly on three things: how much energy the battery holds (kWh), how much power the motor is drawing (watts) and how fast the boat is going. Hull shape, weight, wind, waves and current come on top. That is why manufacturers always quote their figures with a test boat, from a kayak to a daysailer.

The basic sum is simple: running time = battery capacity ÷ power. ePropulsion does exactly this in its manual: a 3,000 Wh battery lasts about one hour at full power with the Navy 3.0 Evo (ePropulsion manual Navy 3.0 Evo, p. 14). Range is then running time multiplied by speed. Because power rises much faster than speed, range collapses at full throttle.

How far do small outboards up to 2 kW go?

Small outboards with a 0.6 to 1.5 kWh battery cover 20 to 171 km at slow speed and only 7 to 13 km at full throttle. These are the manufacturers' figures:

The very high figures only apply at walking pace and in light boats: the Travel Ultralight manages 171 km on a kayak at 3.2 km/h, which is more than 53 hours on the water. For the Spirit 2, ePropulsion counts from 100% down to 5% charge. Which motors belong in this class and what they cost is covered in Electric outboards: Torqeedo and ePropulsion compared.

How far do larger outboards with 3 to 6 kW go?

With a separate 4 to 9 kWh battery, the larger models cover 35 to 116 km at slow speed and around 12 to 37 km at high speed:

Torqeedo's table for the Barro 520-SL does not name a battery; the product page recommends the 5 kWh Power 48-5000. Note that for the Cruise 6.0 on the Barro, Torqeedo quotes more distance at full throttle (20 km) than at half throttle (18 km), and for the Navy 6.0 Evo ePropulsion quotes more at 4,000 W (41.7 km) than at 3,000 W (39 km). Once a light boat gets onto the plane, going fast can become slightly more efficient again. Displacement boats such as sailing yachts never get there.

How long do electric boats with an underwater motor run?

For permanently fitted underwater (pod) motors, the Austrian manufacturer Aquamot quotes running times rather than distances. With Aquamot batteries of 12 V and 260 Ah each (number in the table), the motors run this long:

Sources: product pages Trend 2.2 UF, 4.3 UF, 6.0 UF, 8.0 UF, FAQ in each case. Aquamot does not state the capacity in kWh; by our calculation four 12 V, 260 Ah batteries hold 12.48 kWh together. Aquamot gives no speeds for these running times. As a rule of thumb for the power you need, Aquamot suggests 1 to 2 kW per tonne of boat weight, depending on the hull and with a reserve for wind and waves (Aquamot). These motors power, for example, the licence-free boats in Leines and MY-Electroboat compared.

How much electricity does an electric boat use per kilometre?

At slow speed a small boat uses around 10 to 80 Wh per kilometre, at full throttle 100 to 250 Wh. That is our own calculation from the manufacturers' tables, power divided by speed:

• ePropulsion Spirit 1.0 on a 12 ft aluminium boat: 35 W at 3.5 km/h is 10 Wh/km, 1,000 W at 10 km/h is 100 Wh/km (ePropulsion).
• ePropulsion Navy 3.0 Evo: 300 W at 6 km/h is 50 Wh/km, 3,000 W at 16.4 km/h is 183 Wh/km (ePropulsion).
• ePropulsion Navy 6.0 Evo: 500 W at 6.5 km/h is 77 Wh/km, 6,000 W at 24.3 km/h is 247 Wh/km (ePropulsion).

Twice the speed costs several times the electricity per kilometre. If you know your route, plan with cruising speed, not full throttle. Where you can charge along the way is shown on our charging map for electric boats.

What do watts, input power and efficiency mean?

The wattage on the spec sheet is usually the input power, the current the motor draws from the battery. Less arrives at the propeller. For the Cruise 6.0, Torqeedo states a continuous input power of 6,000 W and a nominal shaft power of 4,900 W; for the Cruise 3.0 it is 3,000 and 2,300 W (Torqeedo Cruise manual). ePropulsion states the maximum overall efficiency: 55% for the Spirit 1.0, 51% for the Navy 3.0 Evo and 48% for the Navy 6.0 Evo (manual Navy 3.0 Evo, Navy 6.0 Evo). Aquamot quotes 92% motor efficiency for its Professional pod motors, without the propeller (Aquamot brochure).

For range, input power is what counts, because that is what drains the battery. Whether you need a licence depends on the country and, in Germany, on the motor's power; the limits across Europe are in Electric boat without a licence.