Electric outboards, thrusters and pods

Backed by predictions that more electric vehicles (EVs) will have a 400+ mile range by 2025, the marine industry continues to move steadily towards electric propulsion. Whilst the initial price of electric outboards, thrusters and pods remain high due to the batteries required, over time the investment pays back in lower (if any) maintenance costs and a longer lifespan. There are simply far fewer components to corrode or wear out. For many, apart from dedicated petrol-heads, the real value is that boating becomes more enjoyable through near-silent and fume free propulsion. There is also the opportunity to become greener by recharging through renewables, particularly solar. Some OEMs such as Aquamot, Torqeedo and ePropulsion even sell dedicated portable PV panels, carefully matched to their proprietary batteries. Many outboards also offer a degree of hydro regeneration when under sail, although some speed is required (usually 6 knots or more, but the threshold is getting lower). US-based Forza even offers ‘regenerative stopping’ to harness a few watts from momentum.

Thanks to more efficient production methods and economies of scale, capital costs continue to trend downwards. Much of the progress is being made in China, where sales of EV’s topped 4.4 million in 2022, meaning 22% of passenger vehicles sold domestically that year were all-electric. A good example of increasing capacity is from Suzhou Energy Technology Co ltd, makers of the ExploMar range of electric outboards. CEO Alex Dong explained that improved manufacturing and distribution infrastructure is accelerating production and making the motors more affordable. “ExploMar has introduced three powerful electric outboards – the Wave 300, Wave 150+, and Wave 70+,” he says. “In January 2024, we finished building our ‘intelligent’ manufacturing base in Changshu, China. This is equipped with mass production lines and warehousing logistics for delivery and shipment. Our goal is for everyone to experience the thrill of electrification and intelligent driving while keeping our oceans, rivers, and lakes clean from pollution. We believe more and more distributors will join our sales and service networks. “

Another Chinese OEM paving the way to lower costs is Parsun, a company already well known for its four-stroke gasoline outboards, but also developing a full range of electric alternatives.

“We are building a new factory for high-horsepower four stroke outboards, electric outboards, and other new products,” says Nathan Zang, VP of sales for Suzhou Parsun Power Machine Co Ltd. “It will be equipped with industry-advanced flexible production lines, AGV logistics and distribution system, and a modern warehouse management system. Also under construction are a series of laboratories dedicated to component validation, environmental testing, electrical safety, and anti-salt-mist corrosion.”

Both c and Parsun say they have developed state-of-the-art R&D facilities to enhance the innovation of electric propulsion systems.

An Autumn of takeovers

With other manufacturers gearing up to harness economies of scale, future growth looks certain. As a result, the sector has recently seen significant investment and several high-profile take-overs. Perhaps the best example is the German manufacturer Torqeedo, one of the earliest pioneers of electric outboards and now a wholly owned subsidiary of Yamaha. As a huge and diverse Japanese OEM, Yamaha had previously launched its revolutionary Hymar 10kW outboard, an electrically steered pod that could fit neatly beneath a bathing platform. Now the company can combine Torqeedo’s accumulated knowledge with its own track record of gasoline outboards, harness them to a large manufacturing base and take both brands forwards.

Meanwhile, Temo, the French OEM who came to prominence with a battery-packed 250W motorised pole, has just received €6m of additional investment. This will finance further product development, which recently included the slim profile Temo 1000. Over in Canada, Vison Marine Technologies, who produce the conventionally styled E-Motion 180-E outboard, has closed a US$3m deal with backers Investment Quebec. CEO Alexandre Mongeon says the financing will allow the company to develop its latest product and create 24 new jobs.

Back in Germany, marine motor makers Molabo, which keeps all its products within the ‘touch-safe’ 48V architecture has just been bought by one of its earliest supporters, the Herchinger Group. Behind some of these takeovers is a view to exploring other sectors, particularly e-mobility. Yamaha, for example, is keen to develop new motor technology for both land and water, the company’s new Tricera concept vehicle offering a glimpse of the future. It’s the same with Molabo. The ISCAD motor design (Intelligent Stator Cage Drive, where traditional motor windings are replaced with metal bars) provides a great deal of power for a comparatively low voltage. This lends itself to several automotive applications, something the Hechinger Group has realised. As CEO Markus Duffner explains: “The production of drive systems will be increased in order to prepare for expansion into the industrial and, in the long term, automotive sectors. Molabo will be taking on a central role in product development within the Hechinger Group.”

Faster to market

Assisting the rapid development of electric outboard systems is the compact and self-contained nature of the BLDC (BrushLess Direct Current) motor, which is already mass produced for other sectors. This makes the journey from concept to realisation much shorter, a process aided by standardised plug-and-play electronics and a wide choice of control systems. Advances in design simulation technology and computational fluid dynamics allow inventors to test their ideas ‘virtually’ and avoid the costs of multiple prototypes. When prototypes are required, the various pieces are easy to make as one-offs using

3D printers.

Something IBI is noticing is a converging of ideas. The industry seems to be reaching similar solutions in terms of efficiency, user interface, complete system packages and portability. The biggest issue remains the battery, which effectively doubles the purchase price of the engine. “People aren’t used to paying for fuel up front,” said Eclass’s Lynelle Johnson. “If you compare the lifetime cost of a petrol outboard with an electric one, the difference is eye-watering. Over 10 years, an owner could spend AUS$ 50,000 (c US$ 33,000) in fuel.”

ACEL, a Canadian-based OEM, echoes this sentiment, although with a more conservative figure. “We estimate an electric outboard user saves about US$9,940 over five years based on normal usage,” their literature states.

Some OEMs opt for a proprietary battery that is perfectly matched to their product, as cheaper types could reflect badly on performance. Others, mainly for voltages of 48V and below, allow the motor to harness almost anything of the right output, including different chemistries. Meanwhile, technological advances continue, spurred on by the automotive sector as it seeks the smallest, lightest and most powerful motors available. The axial flux design used for in-wheel drives, for example, has recently exceeded 15kW/kg, with a quadrupling of torque. Not long ago that power-to-weight ratio was in single figures.

Aware that it is still not as green as it should be, the sector has a watchful eye on the raw materials market. There are concerns that China’s domination of ‘rare earth’ mineral deposits, key to essential parts of the motor, battery, and electronics, could hold the industry to ransom. More abundant alternatives, extracted with lower environmental and social impact, are eagerly being sought.

For this feature, we’ve aimed to distil the technical advances that will make a big difference soon and sought to understand the trends within the market itself. One thing is certain - there is a lot going on.

Technical advances

Easier battery recycling

The battery chemistry of choice for electric propulsion is lithium ion, mainly due to its deep-cycle ability, lightweight, high-energy density (now 200-300Wh/kg, and expected to be 500Wh/kg by 2030), long service life and no ‘memory’ effect. There are also several different formulations based on lithium metal, with more being added due to extensive research. The batteries are usually made up of individual 4.2V (peak) cells, which may be pouches or cylindrical cells. Most common are the latter, either ‘18650’ (18mm wide, 65mm long) or the larger ‘27100’ (27mm wide and 100mm long).

An emerging trend now is to make the batteries easier to recycle. Instead of the cells being welded and glued together in clusters, for example, battery designers such as Kahe and Liontron are sandwiching the cells between detachable contact plates. The battery is easy to open, the plates simply pull apart, and the individual cells can be dropped out and replaced. This preserves the casing and the battery management system (BMS) for ongoing use. This approach is very practical as sometimes a whole battery can fail when just one or two cells malfunction within a pack of hundreds.

Proprietary, or third party?

Outboard manufacturers are divided over whether to supply their own battery or allow the buyer to hook up to anything they want. A proprietary battery will have been fully optimised for the motor it serves, with high quality cells and a perfectly matched charger. Many battery fires have been caused by incompatible chargers or the poor quality of the cells, or an unsuitable battery management system (BMS). The big brand names want to ensure that every component is built to a high standard so they can offer an attractive warranty.

Another advantage is that remotely sited proprietary batteries can be linked together in parallel via plug-and-play cables, maintaining accurate monitoring. As is common with cordless power tools, an owner can buy extra batteries and have them on charge or in reserve whilst the motor is being used.

However, a consideration with proprietary batteries is that you are locked in to the brand, an issue highlighted in the e-bike industry where there is a growing call for standardisation. For each brand of bike or outboard, nothing else will fit. (Honda, however, has developed a swappable system between their EM1e scooter and their concept outboard but, again, only compatible within the brand.) Some OEMs have therefore offered the ability to use any brand of battery of the right voltage, and even across different chemistries.

Our customers can use any type of battery – lithium ion, lithium phosphate (li-po), or lead acid, our technology is battery flexible” says Elco’s Dean Heinemann. “One big advantage is that we don’t have to ship heavy batteries overseas as part of the package. Customers can source their batteries locally or use ones they already have, as long as they meet the requirements of the motor.”

There are now many companies offering high quality Lithium-based own-brand batteries in a range of voltages. Some, like the German OEM Rigbee, place them in a waterproof carry case with standard IP67 waterproof sockets and blue tooth enabled monitoring.

Recycled auto batteries

The growth of EVs over the last decade means that many automotive batteries are coming to the end of their serviceable life. Capacity gradually falls from 100% to around 70% over 1,000 or more cycles (anywhere from 3 - 10 years’ use) meaning a significant drop in an EV’s range. These time-served lithium cells, however, can still have a very useful ‘second life’ for less demanding applications, such as marina ‘powerwalls’ (static power storage for renewables) and large capacity banks for small to mid-range outboards.

A specialist in battery upcycling is Australia-based Eclass Outboards, which harnesses discarded EV cells as a cheaper alternative to brand new batteries.

“The charge cycles and voltages may have dropped, but then you don’t use a boat every day,” explains Eclass director Lynelle Johnson. “This means the lower capacity isn’t an issue, especially as the outboards don’t use as much power. But the big thing is that the price is about 40% less than a new battery, so it removes one of the cost barriers to going electric.”

The ability to adopt ‘tired’ EV cells also means that as new battery chemistries come along – and there have been some exciting advances recently – boaters will be able to swap to more modern formulations without paying a premium price.

Composite propellers

For combustion outboards, the propellers are usually pitched to the anticipated cruising speed, harnessing the best of the torque curve for optimum efficiency. The challenge with electric outboards is they have a different torque curve and rev range. There is also the ability in some to hydro regenerate. This has made optimal propeller matching more difficult. An answer has been to provide a choice of cheaper plastic or composite propellers pitched to the application, which also helps to reduce the weight of portable machines. The makers of some of the smallest thrusters even offer plastic folding props and detachable cowlings. A greater number of blades are being added to standard props, too, with more use of swept ‘submarine type’ designs. Every amp is being harnessed by optimal propeller design, especially as hydro regeneration becomes more of a selling point.

CANbus monitoring and control

Electric propulsion lends itself to CAN (Controller Area Network) bus, which is essentially a plug-and-play system centred around a control box. For the boatbuilder, refitter or DIY enthusiast, this makes fitting an electric motor very straight forward, and if the voltage is kept below 48, then no specialist training is needed. (If you get it wrong, you are unlikely to die from electrocution). Outboard manufacturers across the size range are focussing on the simplicity of set-up, and a CANbus link allows the entire system to be monitored via an app. Ever more accurate battery state monitors are allowing users to know exactly how much range they have left. Some OEMs are also introducing a level of autonomous sailing, where the controller will calculate the voyage entered into the GPS and set the output to ensure the battery can achieve the distance. Recharging points are also highlighted on the chart plotter as the voyage commences. Torqeedo, for example, has an app that extends a range ring around a boat’s position to show what destinations can be comfortably reached with the energy available. Even the smallest outboards will have a gauge that will tell the remaining battery percentage with a fair degree of accuracy, although this isn’t guaranteed if different chemistries are used.

Electric steering

Not new, but increasingly common, is built-in electric steering. This is particularly useful on directional thrusters as they can be literally rotated through 360-degrees via a joystick. The main advantage of electric steering is that it is much easier to install as no heavy steel cables or hydraulic rams are needed, just a CANbus link. The steering is also easier to interface with an autopilot, as the servo is already in place, and several OEMs are now introducing a greater level of remote piloting into their drives. An example is ePropulsion’s new X Series. which can use the outboard as a thruster to maintain a heading or position.

Evoy, a specialist in large and powerful outboards, is taking electric steering a stage further by partnering with Zeabus, a leading provider of autonomous navigation solutions. ‘We see a tremendous opportunity in this partnership,” says Evoy CEO and founder, Leif Stavøstrand. “The future requires betting on electric vessels and AI now. Self-driving electric boats are more flexible, are energy and cost-effective, and sustainable solutions across the board.’ Testing will begin this spring.

More efficient recharging

Smaller outboards. of up to 10kW/48V can usually be recharged, albeit slowly (6-8 hours) from a standard 13amp 240V/110V AC outlet, the type commonly found at marinas. In some areas of the world, the electricity supply to the berth is part of the visitor’s fee, adding to savings in running costs. The batteries can also be charged via onboard renewables during - and between - outings. Several OEMs now offer a raft of recharging possibilities, with the onboard electronics able to take inputs simultaneously from wind, solar or even a fuel cell. For the larger outboards, those running anywhere from 96V to 800V, a dedicated fast charger is needed for a quick (30mins-1 hour) top-up. Although the network for fast marine recharging is growing, spearheaded by companies such as Aqua superPower, it is still in its infancy. In the shorter term, many power electronic suppliers and makers of battery chargers are seeking to make the low amperage recharging more efficient, and therefore quicker, with minimal risk of fire or battery damage. Specialised chargers, such as that found in the Swedish Stream outboard system, allows a large and high voltage battery to be charged from a standard 240V marina outlet, providing the skipper isn’t in a hurry.

Better motor sealing

Electric outboards divide into two main types, ones with the motor above the waterline, and the other with it below. For underwater housings, the sealing is critical, as a saltwater leak will quickly write-off the motor. Usually, the sealing is so good that the motor can remain untouched for years. A good example is ePropulsion’s new X series, which is warrantied for 5,000 hours, which, based on the average of 50 hours motoring per season, means around 100 years. A dealer for Torqeedo said that the only time the seals were compromised was when the propeller was hit hard on an underwater obstruction, a problem common to all outboards.

The Chinese manufacturer Fuber, which is planning the launch of its Global 1.0. Global 1.5, Global 30 and Global 40 models this year, has developed a new transmission on its two smallest motors to help enhance seal integrity.

“The Global 1.0 and Global 1.5 are suitable for smaller boats and adopt magnetic coupling sealing technology,” says Zhinde Lee, sales president for Tianjin Fuber Technology Co Ltd. “Their structures do not have rotating shafts and shaft seals, achieving contactless and leak free torque transmission. Compared to other electric outboards in the market, this has solved the easy leakage of underwater rotating sealing structures. This makes our products more cost-effective and the appearance more exquisite.”

More use of foils

The best way to increase range is to lift the boat out of the water, and the use of foiling technology is being rolled out right across the e-drive sector. It is perhaps most notable at the smallest end of the market, where there has been an explosion in small, electric craft and surf boards that can foil, effectively doubling both speed and range in the process.

Key to the success of electric foiling is the torpedo-shaped motors, which don’t need to be particularly powerful, and strong blue tooth connectivity, meaning the rider can use a wireless controller. The quick acting inertial navigation electronics developed for drones can keep the boat – or board – ‘flying’ by making several adjustments per second. The active foils are constantly twitching in response, so no piloting skills are needed – just steer, and leave the ‘flying’ to the computer.

Magnetic kill cords

Almost a standard fit now on electric outboards is the magnetic kill switch, which also acts as an anti-theft device. Little more than the size of a key fob, sealed and buoyant with no battery required, they simply drop into a receptacle by the throttle, and easily detach in an emergency.

Better cooling

When heat builds up in either a battery or electric motor, the atoms in the conductors get ‘excited’ and start blocking the path of the fast-moving electrons. This creates resistance, which lowers efficiency, the reason why superconductors are kept as cold as possible. On smaller outboards, the motor tends to be fully immersed in the waterflow which draws the heat away, with the battery and electronics topside cooled by the air. In larger outboards, extra cooling is needed. Several OEMs have opted for a closed loop cooling system, meaning that no corrosive salt water has access to the innards of the motor. Instead, a heat exchanger is in the drive leg. On larger battery packs, the same principle is used, with the closed loop extended around the cells.

System wide approach

For a system to work efficiently, everything must be compatible, so many outboard OEMs opt for a system-wide approach. Every component has gone through extensive R&D testing and evaluation before becoming part of the installation. Many of the power electronics used are industry standard, with companies like Mastervolt, Victron, Dolphin Chargers, C-Zone and Piktronics supplying high quality connectors and controllers designed specifically for marine applications. Internet connectivity also allows the OEMs to dip into a system remotely (with owner consent) and check everything is as it should be. No need to send an engineer if the diagnostics say the boater has simply kicked out a plug.

A big advantage of this type of installation is that advanced electronics can be built in, giving the owner a wide range of options for navigation and energy monitoring. In technology developed for trolling motors, which aim to keep the angler directly over their favourite fishing spot, even quite small outboards are now able to link to a GPS and stay in one place.

Rim drive revolution

Widely used in commercial vessels, the RIM drive houses the stator in the sides of a tunnel, lending this type of motor ideally to outboard and thruster applications. The big advantage is the propeller is automatically protected and any debris that gets entangled is usually self-clearing. One user remarked that if the prop gets fouled, they just stop motoring and the flow of water through the tunnel causes the debris to just float away.

One OEM successfully harnessing the rim drive is Blue Nav, a French company that has made a directional thruster that can retract, and so allow a boat with conventional engines to add an electric drive without major surgery. The steerable motors also double as stern thrusters, making for easier docking, and can provide gentle cruising for several hours under their own batteries. The company has recently added an autopilot function in addition to joystick manoeuvring.

Conclusions

The electric outboard sector is changing fast as electric motors, batteries and controllers continue to evolve, with downward pressure on pricing enabled by mass production and heavy investment in the EV sector. The ‘green’ credentials are also attractive to the buying public, although these motors and batteries are not quite as sustainable as they imagine – yet. Some advocates within ICOMIA even suggest that it will be greener to convert existing combustion engines to run on sustainable fuels than to develop new battery chemistries from rare earth minerals. Portability via battery detachment remains an attractive option with smaller outboards, whilst low maintenance, silent running, zero pollution and the option to recharge from renewables makes economic sense across the power range. However, the large capital costs of buying a decade’s worth of fuel up front remains a challenge.