Is Electric Propulsion the Future for Boating?

Everyone’s jumping on the all-electric bandwagon, but some argue that today’s systems are not a realistic solution for the needs of many mariners. Other alternatives, however, hold promise.

Boats have never been known for their awesome fuel economy, and today’s waterborne equivalent of a Toyota Prius gets worse mileage than a 1975 Buick Electra. Hey, it’s not their fault—boats have a heckuva lot more friction to deal with than cars, and they can’t exactly coast downhill for miles on end. Electric boats make sense in a few applications, but range and speed are drastically limited with today’s battery technology. None of this, however, means that the marine industry is resigned to building boats that endlessly chug mass quantities of fossil fuels.

Biofuel in Boats

The National Marine Manufacturers Association paints the picture this way: There are around 12 million registered boats in America, and most are powered by internal combustion engines. The life expectancy of a boat is 20 to 30 years. So, these boats will be around until 2054, and they need a liquid fuel that’s compatible.

Biofuels such as butanol might be one alternative. Butanol has been tested in boats since 2012, when several industry players teamed up with the NMMA, Argonne Laboratory, and the US Department of Energy to run butanol through a number of marine powerplants at a 16 percent mix. Not only was it a viable alternative, but it also didn’t absorb water and remained stable after blending, unlike ethanol. The NMMA officially approved the fuel in 2015, and it also has the EPA’s blessings at a 16 percent blend. However, thanks to issues including distribution, additional approvals, and higher cost, butanol is still unseen at the marina pumps and remains a fuel of the future.

Gasification

Another fuel that hit the water recently is natural gas. In 2015, Blue Gas Marine rolled out conversion systems that are specific to different model outboards but can work with engines made by all major manufacturers. They also have a diesel-hybrid-mix system (70 percent natural gas, 30 percent diesel fuel).

While the boats using these systems might require some significant retrofitting, particularly to incorporate gas tanks, the bigger barrier to adaptation again remains the availability of fuel. On the flip side of the equation, not only does running on compressed natural gas vastly reduce your carbon footprint, but it also costs less. Blue Gas claims its systems reduce fuel consumption by 40 percent and overall running cost by 70 percent.

High on Hybrid

The hybrid electric-gasoline solution that works so well in the automotive realm doesn’t provide as much benefit in marine systems due to the same range and speed drawbacks of purely electric power. Still, hybrids sometimes prove advantageous.

Displacement and semidisplacement boats can cruise for limited distances on electricity before firing up internal combustion. Sport-fishing boats that troll for hours can use their diesel powerplants for high-speed, long-range runs and switch to electric power while fishing. And some of the newest hybrid systems can even incorporate both types of power at once for a performance boost.

E-Motion’s parallel hybrid system, for example, has a Power Booster mode in which the electric and diesel motors both kick in at the same time to boost acceleration by 25 percent and top end by up to 3.5 knots. But like they are in the automotive world, hybrids seem likely to be a bridge solution as opposed to an endgame.

Mixing and Matching

“Yamaha is proposing a multiprong solution,” says Martin Peters, Yamaha division manager for marine external affairs. “There are applications where electric makes a great deal of sense, and we have electrified product (the Harmo) at the low-horsepower end. The problem with electrification at this point is that batteries don’t have the energy density close to providing the range most people expect for a boat.”

The gap in energy density between gasoline and even the latest batteries is huge. Of course, batteries are constantly improving. But until the tech is sufficient, Peters points to biofuels as one alternative, and says another might be a fuel source we’ve seen in experimental use: hydrogen fuel cells. “Yamaha in Japan has been working on automotive engines with Toyota,” he says, “developing hydrogen power for internal combustion.”

And, About Electric…

In certain niches, specifically those that don’t require tremendous range or blistering speeds, electrification is here. “We’ve seen steady sales the past few years,” says Brandon Gross, president of ElectraCraft, a company that has built small electric boats since 1975. “And now with all the solar options and lithium-ion batteries, charge times can be cut in half and range about doubled.”

Meanwhile, several electric up‑and‑comers, including Candela, Pure Watercraft, Quadrofoil and Epoch, are leveraging tech such as retractable foils and LiFePO4 battery banks to diminish the range and speed limitations of electric-powered boats. Candela claims it can attain a range of about 58 miles at 23 mph.

Will all-electric powerplants eventually replace internal combustion on boats? Perhaps at some point. But at least for the foreseeable future, expect these other alternatives to bridge the gap.