Nathan Eddy // Contributing Writer

Boat manufactures around the world are ramping up production of electric watercraft ranging from pontoons to speedboats. They’re turning to batteries to produce emission-free products that deliver on range and speed.

The move to electrify recreational boating has attracted traditional industry heavyweights such as Brunswick Corp. and Mercury Marine Corp., plus a variety of startups.

The market for electric leisure craft continues to grow at an increasing rate as more boat owners make a deliberate choice between conventional internal combustion engines (ICEs) or a quiet, clean drive technology.

Among the key benefits of electric drivetrains are fewer moving parts, no engine oil or gas to deal with, less winterization requirements, and an overall reduction in the number of maintenance issues and trouble spots—all which contribute to prolonging the life of the drivetrain.

The benefits of an electric drivetrain extend to the comfort and convenience of the owners and passengers as well. Electric boats are virtually silent, and the removal of the ICE also removes exhaust fumes.

Despite all these benefits, EV boat manufactures are up against several challenges, from the weight of batteries to the high resistance a vessel encounters when plowing through the water.

The propulsion system, including high-voltage batteries, motors and propellers, typically need to be designed from scratch due to poor off-the-shelf offerings. Achieving acceptable range is also a huge challenge, because of the high drag between boat hulls and water.

“To maximize efficiency, the entire boat needs to be designed around electric propulsion, rather than retrofitted, which adds cost,” says Luke Gear, principal technology analyst at IDTechEx. However, he says there have been some novel approaches to address this issue, including the use of hydrofoils.

So far, growth has been slow and steady, and is not taking off in the same way as other electric vehicle segments, such as passenger cars (or even categories within the marine sector, such as ferries and offshore support vessels).

Part of the apathy toward restricting boating emissions is because of economies of scale. While emissions per outboard can be over 30 times the emissions per car, the scale of the problem is still much smaller. Fewer than 500,000 outboards are sold annually vs. roughly 80 million automobiles.

Efficiency Gains from Hull Designs

One company at the forefront of the electric boat trend is Boote Marian GmbH, which is based near Salzburg, Austria. It produces six models that are powered by lithium-ion batteries with up to 125-kilowatt hours (kWh) of power, which enables them to reach a top speed of 39 mph. The company recently took the wraps off its 26-foot M 800 Spyder, which offers 150 kilowatts (kW) of power.

Marian has focused exclusively on electric boats since it was founded 22 years ago. And, the company prides itself on matching electric drives to the efficiency required from hull designs.

For instance, the hull of the M 800 is designed to give the boat greater range and optimize its top speed. The unique shape helps the boat plane at lower speeds, while also providing better efficiency at higher speeds.

One major difference in the design of an electric boat compared to an electric car is that engineers cannot rely on the energy recuperation typical of road vehicles.

“We only actively consume energy while driving and cannot recover it,” explains Samuel Keller, marketing and media director at Marian. “Due to the additional relatively high frictional resistance of the water, we need significantly more battery capacity and therefore more space for a range comparable to that of today's electric cars.”

That’s why when designing e-boats, engineers must consider hull designs that are perfectly matched to the electric drive. Marian uses a system consisting of a battery, motor and semiconductor.

Depending on the model, Marian offers its customers a variety of different battery configurations, with parameters such as the size of the boat and the type of hull (for example, a displacement hull or a planning hull) primarily determining the battery systems available.

With the M 800, Marian gives consumers a choice of two battery systems—one with a 150-kW motor and one with a 125-kW/h battery capacity. With the Capriole 700 model, which is based on a displacement hull shape, electric motors up to 100-kW can be selected.

According to Keller, manufacturing challenges include the generally low availability of battery systems, high raw material prices and above-average delivery times. “However, we are already in lively exchanges with numerous developers of the various systems, so we can offer our customers the latest and most efficient technology in our models in the future,” he points out.

Marian is currently assessing “promising” attempts to integrate specific charging infrastructure for electric yachts at marinas and ports.

“In particular, the expansion of so-called supercharger systems like what you see in the automotive industry can already increase the range of our boats to such an extent that they represent an alternative to combustion engines,” says Keller.

Using Solar on the Sea

Another European boat builder quietly making waves is Silent Yachts, which specializes in catamarans ranging from 59 to 112 feet. To address recharging challenges, its boats are covered in solar panels.

“On a catamaran, you can produce enough energy to power the entire vessel,” claims Michael Köhler, CEO of Silent Yachts. “We do not refit an existing [boat] to be fully electric, as this would only bring a lot of unwanted compromises. Instead, we start with a clean sheet of paper.”

The solar panels produce energy that is stored in lithium-ion battery banks. This energy can then be used to power the electric propulsion system. It also supplies power to all the household and navigational appliances on board. As a result, there is no need to run a generator when the yacht is anchored at bay or docked in a marina.

Two of the main criteria for the development of an electric boat are weight and efficiency. The lighter the yacht, the less energy is required to move it.

“[With our boat], excess energy can be stored in the batteries as power reserves,” says Köhler.

“Additional design features, such as shaded windows, thermally insulated cabins and energy-efficient kitchen appliances, make sure power consumption is reduced to a minimum," Köhler points out. "All these factors combined create a solar-powered yachting experience without comprises, zero emission and virtually unlimited range.”

Silent Yachts recently expanded its product line with a hybrid boat designed and built together in collaboration with partner VisionF Yachts. In addition, the company is launching a range of electric tenders (smaller craft that run back and forth from a larger ship).

Köhler believes the adoption rate for electric boats will gradually increase, similar to what has happened in the automotive industry over the past decade.

“The matter of sustainability is omnipresent nowadays, and rightfully so,” says Köhler. “However, instead of telling people to stop doing what they love, we need to provide them with options to continue to follow their passion in an ecofriendly manner. Solar-powered yachts combine the best qualities of two opposing approaches into a single boat.”

Electric Outboard Concepts Surface  

For decades, Mercury Marine engines have been the go-to source of power for generations of boat owners. The 83-year-old company, which traces its roots to a small machine shop in Wisconsin, has been focusing recent R&D efforts on electric power. Earlier this year, Mercury unveiled the Avator electric outboard engine at the Miami International Boat Show.

It is designed for use with a wide range of pleasure craft, including dinghies, fishing boats and pontoons. Mercury plans to bring the portable electric outboard to market next year, following in the wake of other manufacturers, such as ePropulsion, Torqeedo and Vision Marine Technologies.

“Electrification is strategically important to us, and this concept provides a first look at how we intend to deliver on our commitment to being the industry leader in both internal combustion products and electric propulsion,” says Chris Drees, president of Mercury Marine, a division of Brunswick Corp. “We are taking efficiency to a new level, opening up new ways to enjoy the boating experience.”

“We see growing demand for electric outboards, especially in the low horsepower segment, where the benefits of electric can be realized at competitive prices,” adds Alex Cattelan, chief technology officer at Brunswick. “As the leader in recreational marine propulsion, electrification is strategically important.

“Electric propulsion provides unique performance, including quiet and smooth operation, zero direct emissions and ease of maintenance,” notes Cattelan. “We are developing the Avator concept to take full advantage of these benefits while efficiently managing on-board battery energy.”

According to Cattelan, there are many similarities in the design and assembly of ICE and electric outboards. Mercury Marine also plans to leverage its long-standing knowledge of compact packaging and intuitive operations.

“For the Avator concept, we also integrated unique display, communication and connectivity [features] we expect to appeal to our customers,” says Cattelan. “On the manufacturing side, commonality includes efficient and repeatable processes with precise measurement and controls.

"We have used these common principles in the design and assembly of outboards for years,” explains Cattelan. “The Avator products will integrate these principles with the unique aspects of the electrified propulsion system.”

When Mercury Marine was founded, the company started with smaller outboards and then gradually evolved into higher-horsepower products as the market matured.

“We anticipate similar development for electric propulsion systems,” says Cattelan, noting the market for low-horsepower products is already established and growing rapidly. “We see an opportunity to be disruptive in this space and provide consumers with an elevated experience.”

Cattelan believes Mercury’s decades of experience manufacturing and assembling outboards, coupled with its acquired skills at battery assembly, will ensure that it can address the unique aspects of electrified propulsion, from thermal management and energy efficiency to safety.

In addition to electric propulsion demands, Cattelan sees a need for higher capacity energy storage and power management systems to support growing electrical content of marine applications such as accessories and control systems.

That’s why Brunswick has been innovating and investing in electrified energy storage, including Mastervolt and ReLion batteries, as well as Simrad and CZone propulsion, communication and control systems.

“The Avator concept is our first step in our electrification strategy,” says Catteln. “We’re focused on developing a full portfolio of electric products over multiple years.”

Balancing the Pros and Cons of Battery Weight

Arc Boat Co., a Los Angeles-based startup founded last year by a group of former SpaceX engineers, is planning to deliver a handful of limited-edition battery powered, aluminum hulled boats boasting a top speed of 40 mph. Its 24-foot Arc One will cost more than $300,000. But, the company claims that it will be “far more reliable, cheaper to operate and maintain, quieter, quicker and more seamlessly integrated with software than any gas boat.”

Arc designs and builds its speedboats in-house, including battery packs, power train systems, thermal control systems and software.

A fast craft like the Arc One requires a large battery. With 220-kWh, the battery, which weighs nearly 3,000 pounds, offers three times the capacity of a Tesla Model Y—at nearly three times the size. The company estimates that it will supply enough energy for three to five hours of use. The battery’s weight is used to establish a low center of gravity for the boat and provide a smooth, stable ride.

“The design of the boat and the battery have been heavily intertwined from the very earliest design stages,” says Ted Herringshaw, head of product at Arc Boats. “This is one of the benefits of our approach to building for electricity from the beginning, as opposed to retrofitting a gas boat.”

Boats need more energy than cars do, since they constantly encounter resistance while moving through the water. However, cooling, which is one the biggest challenges with electric vehicles, is easier when you can use the surrounding water. Charging patterns are also friendlier for boats—closer to the way one would use a phone rather than a car.

“A boater typically goes out for one long session, followed by one long overnight rest at a familiar location,” explains Herringshaw. “In a car, you'll mix in more starts and stops in different locations throughout a day, along with longer road trips.”

Another major concern is waterproofing. Herringshaw says all Arc battery packs and electrical systems are watertight, heavily reinforced and constantly monitored. “Luckily, we’re not the first ones that needed to solve this problem,” he points out, noting that electric cars also operate in volatile, wet environments. “There’s some prior learning we can build on in this area.”

Within the next few years. Arc plans to expand its product portfolio and produce more affordable, mass-market boats to help electrify other segments.

“We believe electric boats are better than gas boats in nearly every dimension,” notes Herringshaw. “This is what gave us conviction to start the company. We’re excited about the number of maintenance-related headaches we’re removing, too.”

Sustainability Drives Demands

However, low maintenance is not the only aspect of sustainability that’s driving growth in the electric boat industry. More countries, such as Austria, Germany and Switzerland, are regulating the number of ICE boats that are permitted on lakes.

“You’re not polluting the air with CO₂, or the water with oil and gas,” says Herringshaw, adding that quieter boats also help reduce the noise impact on marine life. “The industry is just starting to think seriously about electrification, and tailwinds from the auto industry will help push that thinking forward quickly with boaters. We’re excited to watch the market develop and grow.”

The overall market for pleasure craft has been growing recently, partially due to the COVID pandemic. Some people have more leisure time, while others want to spend more time outdoors.

“This is also translating into electric boating,” says IDTechEx’s Gear. “There is currently a strong value proposition in low outboard power classes, but at higher power classes the cost advantages and value erode quickly.”

Gear believes high-power segments will only truly transition with a push for stronger emissions regulation or policy, which is currently lacking in the pleasure craft market, because it’s a much lower priority compared with on-road sectors.

“I think the first challenge for electric boating is the power train—boosting production volumes and lowering costs,” says Gear. “When this market reaches greater maturity, boat makers can start to look at improving the system and energy independence.”

Brunswick, a leading producer of boats with brands such as Bayliner, Boston Whaler and Sea Ray, is bullish on battery power, because it can could improve access to boating in areas where traditional fuel sources aren’t available or allowed. The company sees future growth in demand for electric propulsion, especially as charging infrastructure and battery technology evolves.

“As boating has increased in popularity over the past several years, more consumers are looking to get on the water,” claims Cattelan. “If we can help them find new areas to explore by providing a quiet, simple propulsion solution and one that is sustainable, everybody wins.”

Getting Out of the Water

Swedish boat maker Candela Technology AB has risen to the efficiency and power challenges—quite literally—by choosing to move forward with a hydrofoil design that lifts hulls completely out of the water. It results in a craft that meets both the power and longevity of use demands of mass-market boat buyers.

Mikael Mahlberg, an engineer responsible for product development and communications at Candela, says an electric boat equipped with a conventional hull isn’t optimal using current lithium-ion battery technology. “This was the reason why we realized we must lift up the hull above the friction of water to make a boat that can compete with fossil- fueled vessels,” he points out.

To accomplish this task, Candela turned to engineers from the aerospace industry to design the hydrofoils, drivetrain and carbon fiber hull. The company’s first prototype, the C-7, was followed by the C-8, which solves many of the stability issues that plagued the C-7.

Once the 28-foot boat reaches a speed of 16 knots (18 mph), two retractable foils lift its hull out of the water, greatly reducing hydrodynamic friction. As a result, one charge of the battery pack is good for a range of 50 nautical miles at a speed of 20 knots.

A digital control system automatically adjusts the carbon fiber foils to keep the boat level and steady, even in adverse weather conditions. The foils and propulsion unit are retractable for trailering, storage and shallow water operation.

Candela has received more than 100 orders since launching the C-8 concept and plans to begin delivery later this year. By 2024, it expects to be making 400 boats a year. Candela also recently unveiled an urban water taxi dubbed the P-8 Shuttle.

With the C-7 model, the motor was above the waterline in the casing, followed by a transmission that went through a shaft to the propeller. This system resulted in efficiency losses of around 5 percent, as well as considerable rattling noise.

“If you have an electric boat, it doesn't necessarily mean it's totally silent,” says Mahlberg. “Once you take away the internal combustion engine, you still have rattling from the gears and you also have slamming from the water.”

A big step forward was the development of the C-POD, a direct, all-electric drive, shaped like a 4-inch diameter torpedo. It contains two ultra-compact permanent magnet motors under the water. The system provides enough thrust to give Candela’s boat a top speed of 35 mph, and the electric direct-drive design means there is no noise from gears, or the need for oil changes and other maintenance.

“If you move the motors underneath the water and make them really, really small to fit them into a pod, then you have direct electric transmission with no efficiency losses, and you also get rid of all the noises from the transmission,” explains Mahlberg. “When you start to reconsider how you can make the best marine propulsion, it makes sense to put the motors under the water in this pod.

“You don't need an oil system, because there's no transmission, and you don't need a cooling system,” Mahlberg points out. “You get a slender, easy to maintain design with no service points.”

Candela and other electric boat makers rely on battery packs made by automakers such as BMW and General Motors. Maritime batteries are also sourced from suppliers in China, Japan and South Korea.

“A lot of electric boat manufacturers are buying battery packs made especially for the marine industry, but they're ridiculously expensive if you look at the cost,” says Mahlberg. “Instead, we buy them from an automotive supplier [to get] better energy density and much lower costs.

“Vertical integration of modules and packs will be the best approach in the long term to have greater control of costs and supply, and more tailored designs for the marine environment,” claims Mahlberg.

“To make electric boats mainstream, we have to be able to offer them at the same price point as fossil fuel boats,” notes Mahlberg. “And, if you're sitting at the helm, it's much more fun to drive. You can hear the birds chirping and you can speak to people sitting [at the bow]. There are a lot of benefits to having an electric boat.

“I just compared the C-8 to a gas guzzler yesterday, and it’s much cheaper to drive than an ICE boat,” adds Mahlberg. “I spent 10 euros worth of electricity vs. 490 euros on gasoline for a similar-sized ICE powerboat.”

Candela also plans to produce an electric ferry. The P-12 Shuttle will connect central Stockholm to the outer suburb of Tappström and cut travel time to 20 minutes from nearly an hour. The 40-foot catamaran will carry 30 passengers at a top speed of 37 mph. It will be equipped with the same computer-stabilized hydrofoil system as Candela’s recreational models.

“The leisure boats market is a great business and will continue to be, but I think the main driver for the electric waterborne revolution and the shift to electric transport will be the commercial sector,” Mahlberg points out. “The P-12 will be around 60 percent to 70 percent cheaper to operate.

“One area where you can really squeeze out some results are pleasure boats, because that’s basically a luxury sector,” says Mahlberg. “People driving around for fun in a boat that consumes fossil fuels [may no longer] be viable 10 years from now.”