Two innovative companies at December’s Paris Boat Show presented interesting new electric outboard motors that operate in a fundamentally different way to conventional outboard motor-style units.

Hy-Generation’s RIM6 drive uses a motor mounted in the outer casing of the unit, which increases both torque and efficiency when used with displacement boats.

The case is also shaped like a nozzle, which further increases efficiency, as do the small turbine blades that self adjust for pitch. Overall efficiency is claimed to be one-third higher than for a conventional propeller.

5hp electric outboard motor

The Fin5 is a 2kW (5hp equivalent) electric outboard motor that takes its inspiration from the way fish swim: the motor moves the red disc at the back of the nozzle backwards and forwards in a manner that generates thrust 30% more efficiently than conventional propellers.

This technology is already widely used in industrial fluid transfer pumps. A further advantage is that there are no rotating parts that can endanger people in the water or snag ropes.

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The Fin5, which is equivalent to a 5hp outboard motor, weighs 18kg, including a battery that gives six hours of range at cruising speed and 90 minutes at full speed. Smaller and larger units are in development.

While even the best electric outboard motors won’t suit every boat owner for a very long time, advances such as these will enable more and more to benefit from the quiet running, minimal maintenance and the super-high torque that can make marina manoeuvres much easier than with a diesel.

Fin5 provides propless thrust

How are electric outboard motors tackling range anxiety?

It has already been several years since electric propulsion became the most popular form of auxiliary power for new daysailers and weekenders – we’ve seen it on everything from the retro Rustler 24 and 33 to the RS21 racing keelboat.

While range anxiety remains an issue for many other boat owners, it’s becoming less of an issue for two reasons.

Firstly, year on year battery packs are gaining around 20% extra capacity, with no increase in physical size or cost.

Secondly, manufacturers are improving the efficiency of their electrical propulsion units, whether inboard or outboard.

As well as enabling boats to travel further for a given amount of stored charge, it also makes hydrogeneration – putting power back into the batteries while you’re sailing – more efficient.

Oceanvolt’s Servoprop electric drive

Oceanvolt, for instance, has recently re-engineered its ServoProp series of electric saildrive units to improve efficiency in propulsion mode and to increase battery charge rates when regenerating under sail.

Regeneration now starts at 4.5 knots instead of 5.5 knots, which represents a dramatic effect on charging performance.

The amount of energy needed to spin the propeller fast enough to initiate charging is reduced by a third and there’s a marked jump in charge rates at 5-6 knots of boat speed.

Torqeedo’s new Cruise 3.0 electric outboard motor

6-25hp electric outboard motors

Torqeedo has revamped its Cruise line of mid-range electric outboards, with a completely re-worked electrical design.

As a result power output is up by 50%, yet overall weight is almost unchanged. The new range is offered in 3, 6 and 12kW versions that are equivalent to 6, 12 and 25hp petrol powered outboards.

Similarly, ePropulsion has new versions of its Spirit 1.0 Evo, Navy 3.0 Evo and Navy 6.0 Evo motors, which include a hydro-generating function.

ePropulsion’s new Spirit 1.0 Evo electric outboard motor

3hp electric outboard motor

The Spirit 1.0, which has equivalent power to a 3hp petrol outboard, will run at full throttle for 75 minutes on its internal battery.

At lower speeds, this electric outboard engine can power a 10ft dinghy for as much as 22 miles. When used to power a sailing boat, it will recharge the batteries at 40W at four knots of boat speed, increasing to almost 100W at six knots and a maximum of 300W at 10 knots.

How much do electric outboard motors cost?

ePropulsion Spirit 1.0: from £2,000
Fin5: €3,588
Hy-Generation RIM6: from €6,990
ServoProp 10 system (with 13.3kWh battery bank): from €39,400
Torqeedo Cruise 3.0: £2,999

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This feature appeared in the March 2022 edition of Practical Boat Owner. For more articles like this, including DIY, money-saving advice, great boat projects, expert tips and ways to improve your boat’s performance, take out a magazine subscription to Britain’s best-selling boating magazine.

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