Propelling Our Future: Decarbonization of Boating

NMMA, ICOMIA collaboration puts perspective on electric propulsion, hydrogen fuel cells, and alternative “drop-in” fuels.

De-What? Yes, like the land vehicle industry, the marine industry is getting serious—very serious—about decarbonization—reducing carbon dioxide (CO2) emissions from our boats’ powerplants. Towards that end, the International Council of Marine Industry Associations commissioned a first-of-its-kind study with Ricardo plc, a leading global engineering consulting firm. It found there is not one simple solution. “The boating industry is unlike any other transportation sector and a variety of technology solutions must be considered, from sustainable liquid marine fuels to electric propulsion and hydrogen and hybrid power systems,” said Darren Vaux, ICOMIA President.

You can check out the Propelling Our Future program on the web.

Yes, recreational boating is a small part of the worldwide problem, but that’s no excuse to duck a global effort for our own benefit. BOATING Magazine has long been concerned about the future of our sport.  Everything we do on the water depends on clean air and water in a healthy ecosystem. We boaters now must think about beginning the processes of both adapting current vessels and choosing new ones that fit this brave new low-carbon world. 

The National Marine Manufacturers Association represents 1,249 manufacturers and service providers in the nearly $60-Billion boating industry. The NMMA is working to “get ahead of the curve” because its members recognize that while there is ultimately great value in making this transition, it will be a long, challenging process to re-orient the industry. It will pay to develop solutions voluntarily before they become government regulations. 

There are 12 million boats in the current U.S. recreational fleet, with an annual turnover of only 2%.  Fiberglass boats last a long time (this correspondent’s Boston Whaler Montauk 17 is thirty years old and going strong), and so do most of our powerplants (okay, my skiff has a new outboard). We need realistic solutions now to reduce emissions from our existing boats while the industry develops carbon-neutral boats and engines for the future. Besides benefitting the environent can also benefit boater’s budgets.

Low-Tech, Money-Saving Hacks for Us Boaters Right Now

The first thing boaters can do is optimize the efficiency of existing vessels. Think through how you and your family use your boat. How many hours a day are you actually underway? What speed and power do you need for a satisfactory day? At the simplest level, find ways to burn less fuel and reduce exhaust emissions. Eliminate unnecessary weight, make sure the bottom is clean, have your propeller repaired if its blades are nicked or bent, and run a speed/fuel consumption profile on your own boat like the ones we publish in BOATING’s Certified Tests. Then operate your boat at her most efficient speeds for the conditions you encounter. For any day on the water, plan ahead for the most efficient route and don’t run further than you need to. The effects of these seemingly small changes add up. And, the more boaters that operate this way amplifies the benefits exponentially.   

Yamaha boat propellers
Making sure your propeller is in tip-top shape helps maximize efficiency, and thus reduces emissions. Courtesy Yamaha Marine

Looking Further, to 2035

In the longer term, remember that powering a boat through and over the water is very different from rolling a motor vehicle down a paved roadway.  A marine engine in gear is always under load against a much denser medium than air.  Even if it gets to coast a short distance down the face of a wave, there’s another coming to push against it.  Though electric motors are inherently more efficient than internal combustion, energy storage aboard becomes a crucial element in any long-distance trip, but current battery technology is an order of magnitude lower in energy density than petroleum-based fuels.  ICOMIA’s Ricardo report compares the storage volume and weight of a petroleum fuel tank in a standard powerboat with the volume and weight required for equivalent range and performance with the same boat running a battery-electric or hydrogen-fueled power system.  On that basis, the two alternatives come out way behind.  Progress is coming fast, but right now, there are applications where electricity and hydrogen are not appropriate or present only a partial solution. 

Another wild card is the fact that most of us run our recreational boats only intermittently, averaging just 35-50 engine hours per year.  Even with greater efficiency in electric propulsion systems, their higher initial cost makes them poor choices for such sporadic use.

Two interesting possibilities are “drop-in” carbon-reducing fuels and fully carbon-neutral fuels  that come from renewable sources and can serve our boats’ engines now. Ricardo’s analysis highlights the opportunity to reduce greenhouse gas emissions from boats already in operation, with minimal or no modifications to refueling infrastructure.  What are we talking about?

“Drop-In” Fuels

For the first time, thanks to ICOMIA and the Ricardo report, we have an outline of where the industry might go over the next eleven years. “Now we have data and a timeline to drive specific advocacy for sustainable, boating-appropriate liquid marine fuels, along with the outlines of longer-term strategies with other power systems,” explained Jeff Wasil, veteran outboard industry engineer and current NMMA Senior Director, Environment, Health and Safety Compliance. “Commissioning the study by Ricardo,” he continued, “gives ICOMIA and NMMA the global scientific credibility to promote effective solutions vigorously to policy makers and the fuels industry.”

Yamaha center console
Yamaha is one of many marine engine makers testing “drop-in” biofuels-fuels that reduce carbon and emissions and can be used in current engines without any modification. BOATING editors have run this very boat, and besides a “sweeter” tinge to the exhaust odor, noted no decrease in performance or response. Courtesy Yamaha Marine

Carbon reducing fuels for “spark ignition” (gas) engines, include conventional gasoline mixed with additives derived from non-fossil sources, such as renewable biofuels made from plant waste.  The “feedstocks” for such fuels could be corn stalks, scrap wood fiber, used cooking oil, food waste, or even spent grain from industrial distillation. Current examples of such blended fuels for gas engines include PurFuel 93, which includes 12.5% biobutanol, and VPRacing’s patented EcoGen90, whose 10% non-alcohol additive also comes from renewable sources.  We at BOATING have run biobutanol-enhanced fuel in our own Mercury-powered boats, aboard Yamaha-powered boats, and EcoGen in a Suzuki test boat. We found both to be solid choices for now.

But wait a minute. Fuel from “renewable sources” does not automatically reduce carbon dioxide emissions. To make net progress in emission reductions, it’s necessary to consider the fuel’s “life cycle”. How much energy went into growing the feedstocks? What energy refined it? How did it get to your local fuel pump?  Calculating the life cycle of a “sustainable fuel” is complex but necessary. The U.S. Department of Energy has developed an analysis tool known as Greenhouse Gases Regulated Emissions and Energy Use Transportation (GREET).  It’s available for partners from automakers and oil companies to our friends at NMMA. The website shows the kind of information incorporated in a life cycle calculation. Remember that such calculations must include de-carbonizing industrial facilities, reducing waste, conserving water, and recycling materials.  All contribute to overall efficiency.

We do well to adopt those blended, non-ethanol, NMMA-approved fuels as soon as they become available, but our climate needs more.  In compression-ignition (diesel) engines, Neste offers a Hydrotreated Vegetable Oil (HVO) fuel made from 100% sustainably sourced renewable raw materials such as used cooking oil and animal fat from food industry waste.  This is not a conventional biodiesel.  It involves a full chemical “cracking” (reformulating) industrial process, driven by renewable solar and wind energy. OXE Marine says that running its diesel outboards on HVO fuel can reduce CO2 by 95.8% compared to outboards running conventional gasoline.

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For spark-ignition (gas) engines, Highly Innovative Fuels (HIF Global) produces electricity-based fuels, or “eFuels”, at a pilot plant in southern Chile, with a production plant under construction in Matagorda, Texas and more in planning stages.  If produced using low carbon electricity sources, eFuels are clean, carbon-neutral gasoline substitutes produced from renewable, green hydrogen and carbon dioxide taken from the atmosphere. These drop-in fuels have the same chemical properties as fossil-based fuels, so we can use them now with no engine modifications. They also can be transported the same ways as conventional fossil-based fuels and supplied by current gas stations and marinas. 

Developing Carbon-Reducing Boats

In many ways, the marine power challenge for 2024-2035 is similar to what the infant auto industry faced at the end of the nineteenth century and beginning of the twentieth, experimenting with internal combustion, steam, and electricity for powering land vehicles and boats. 

For your own needs, look closely at the running times and distances for your days on the water in your current boat. You may be surprised to find you don’t need as much range as you thought.  No one is trying to say that electric power is suitable for long runs to fish in blue water.  If, however, you spend most of your time in near-coastal or inland waters, you may find a hybrid diesel-electric or hybrid gas-electric power system makes sense. (If you’re an angler with a bow-mount electric motor, you already have a hybrid system. How much can you use the electric to move around in no-wake zones as well as on your fishing grounds?) 

Volvo Penta has always been known for innovation, so it’s no surprise to find they’re on the cutting edge in a game-changing, integrated diesel-electric hybrid partnership with Beneteau. BOATING’s Editor, Kevin Falvey, described it well in a recent feature. Beyond that partnership, the company’s new IPS Professional Platform features a powerful larger marine drive, the IPS 40. Volvo engineers have designed this drive for dual power input that can employ different combinations of energy sources. The platform can use combustion engines running on renewable fuels, fully electric motors, fuel cell, hydrogen, or hybrid systems. 

Volvo Penta IPS system
Flexible dual power drive system from Volvo Penta–The solution can be installed as a twin, triple, or quad, enabling a mix of power sources to meet the yacht’s needs. Between four and eight power sources from internal combustion engines (ICE) running renewable fuels to fully electric or hybrid solutions, the flexibility to select the type of power source and engine enables unparalleled efficiency. Courtesy Volvo Penta

Another power package is the 450-hp Oxe diesel-hybrid outboard motor introduced at last year’s Consumer Electronics Show.  Oxe Marine is running field tests of the Hybrid 450 on a Nimbus T11. The electric motor is strategically located under the cowling, connected to the drive-belt for seamless operation. Not only does this enhance performance, but it also allows the motor to serve as an alternator, providing the ability to charge the batteries while running in diesel mode.

Developing Carbon-Neutral Boats

There are now fully electric boats with a range of 35-60 nautical miles at speeds around 20 knots, with reserve for running at low speeds and full charging capability overnight. That’s enough daily range for some boaters. While we all dream of long voyages, for most of us, that 30-45 minute trip to a reef, a sandbar, a destination marina, or a favorite restaurant is why we have a day cruiser, a family boat, or an inshore fishboat that can troll silently with precise low-speed control. The most experienced electric marine power company in North America (founded in 1890) is Elco, which offers both inboard and outboard systems. Germany’s twenty-year-old Torqeedo also offers both. Newer companies offering inboards include Ingenity, a subsidiary of Correct Craft (23’ EL Luxury pontoon boat, 27’ Hacker-Craft runabout, and 24’ Super Air Nautique GS22e watersports rig). Others offering outboard power up to 300-horsepower include Vision/Four Winns H2e, ePropulsion, Evoy, Flux/Highfield, and Mercury Avator/Veer

Four Winns H2e
Four Winns H2e, is an example of a model from a mainline boat builder, offered with electric power and suitable for some boaters. Courtesy Four Winns

The new electric vessels are expensive to buy, but the lower “fuel” and maintenance costs of electric power can even that out for some users.  Sweden’s Candela, for example, claims its new 28’ C-8 is much cheaper to run than an equivalent gas-powered boat.  The company says recharging its 45kWh battery is 95% less expensive than gas for the same distance.  That model also made its debut at the 2023 Consumer Electronics Show.  Its retractable hydrofoils and C-POD motor with contra-rotating propellers have far fewer moving parts than any four-stroke diesel or gas engine, require no oil changes, and do not need service for 3,000 hours.

The Candela C-8 is a good example of another valuable trend: developing more efficient hull forms.  When “flying” on hydrofoils at 22 knots, the C-8 draws 25 kW from the battery, whereas a conventional 28-foot electric boat would use more than 100 kW. The C-8 actually planes at around 14 knots as a stepped, semi-V hull, but at 16 knots, it rises onto its foils. There, a computer-controlled system adjusts the foils instantly to suit speed and sea conditions. Six sensors paint a 3D picture of the waves ahead and feed information to electric actuators, which control the angle of the foiling wing. 

Riding on the foils greatly improves efficiency while enhancing the ride and handling in seas up to 4’. A typical planing hull runs with a 4:1 lift-to-drag ratio, whereas Candela claims its actively stabilized C-8 has a 20:1 lift advantage. That benefit shows clearly in the C-8’s wake.  On a short sea trial last fall, we were amazed at how tiny it became when the hull lifted onto the foils. The C-8’s lightweight modern materials also reduce drag and cavitation. So does the C-Pod drive system, specifically developed for this boat.  Combining electric power with computer-controlled hydrofoils is definitely revolutionary. 

Though Candela’s numbers speak for themselves, they are just a beginning. Innovation in marine power and energy systems are accelerating at warp speed. This process will be fun to watch. 

NMMA and ICOMIA logos
The NMMA and ICOMIA are committed to sustainable boating. Courtesy NMMA, ICOMIA


Clean air and water. They are big parts of why we go boating.  The marine industry has a long track record of recognizing that fact. It’s a big part of the revolution in clean, quiet, smooth, and efficient engines—both gas and diesel—that we have seen come to market over the last twenty-five years.  But the effort has extended to all facets of recreational boating, from further engine refinement and cleaner boat construction to coatings like bottom paint, maintenance products, and marina management. 

It’s admirable that companies such as Groupe Beneteau and Volvo Penta have taken a forward-looking approach to product development. With respect to the environment, Groupe Beneteau’s Erik Stromberg, noted his company’s commitment to sustainability, stating, “It’s not just something we have to do. We want to do it.”