An electrifying chat with Mercury Racing’s Stuart Halley.
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We’ve seen a slew of radical electric boating technology over the last few years. From X-Shore’s daycruisers to Evoy-driven Axopars to hyper-efficient hydrofoils from Candela and America’s Cup Emirates Team New Zealand, it’s a fascinating time to be a marine engineer. Few things though, are arguably more arresting than the E1 Series Racebird. Part Galactica Viper, part Formula-E race car and part flying fish, the maneuverable, 24-foot, winged carbon-fiber racer is something else. And while the cockpit, hull and foils are sci-fi evocative, Racebird’s 200-hp electric heart is based on a 2.1-liter internal combustion Mercury Racing motor, only its ICE powerhead has been replaced by electric componentry. When the boat reaches 17 knots, it begins to rise onto its three aluminum foils—one of which is actually bolted to the motor.
Mercury Racing’s General Manager Stuart Halley oversees E1’s motor program. The 29-year company veteran has watched Mercury evolve from carbureted, two-stroke buzzsaws to today’s digitally controlled, supercharged powerplants. A forward-thinking gasoline junkie, Halley has a unique electric perspective on where we are—and where we’re headed.
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Power & Motoryacht: Stuart, can you give us a little insight into how the partnership with E1 Series evolved?
Stuart Halley: Mercury Racing’s part of Mercury. So, we have a history in electric propulsion. Our products have been out there a long time—especially from a trolling motor standpoint. Also, Mercury has announced and shown our Avator electric engine. E1’s high-voltage foiling electric concept was pretty innovative. We decided it was a good a good fit for us. And E1 decided that it was good fit for them.
PMY: Why do foils lend themselves well to electrification tech?
SH: Battery energy storage has come a tremendous way. But one of things that’s different about marine versus automotive is you can gain some battery restoration or charging from braking. Boats don’t have brakes. And then also, rolling down the highway, maybe it’s 35 horsepower to roll a car 60 to 70 miles an hour. It doesn’t take a lot of power versus a boat. One way to reduce vessel drag is by foils. America’s Cup and SailGP kind of machines—they are the innovators. Foils are great for reducing drag, but they’ve got some limitations. They basically start cavitating above 60 miles an hour. That’s why you’ll see limitations right around that 60 mark—which is fine for a lot of applications. I think you can make it an exciting race with 60 mph.
PMY: Can you explain how much less drag say, a Racebird would be generating with foils versus a planing hull? Does that make sense?
SH: Perfect sense. I don’t have that answer, but I do have some rules of thumb on energy storage. One gallon of fuel—that has about the same energy as 11 kilowatts of usable battery energy (a typical Tesla Model S can go around 300 miles on its 100kw battery). So, the batteries need to get about five times better than they are currently to be similar performance to gasoline. But there’s still a difference. Gas burns off and the boat gets lighter—where the battery will always, kind of, be in the boat. Five gallons of gas—which you know, doesn’t send our fast boats very far—that’s about thirty pounds of gas. That battery—to do that same energy as five gallons of gas—would have to be about 1,000 pounds. But as I said, it’s continuing to evolve. But that’s why, I think, it’s being used more abundantly in automotive than marine right now.
The Mercury Racing E1 motor uses an internal combustion-based lower unit with an electrical power head.
PMY: Where can you adapt electric automotive technology, and where does it have to be sort of marine specific? Can you use any old 150-kw motor in an E1 Mercury motor, and a modified battery pack from a Chevy Bolt?
SH: One of the most interesting charts I saw was how the corrosion rate basically increases and decreases as you come away from the shoreline. I don’t remember the exact numbers, but it’s significant. And it just kind of puts an exclamation point on how much more careful you need to be in the marine environment. Our aluminum alloys are all bespoke, and the way we do our electrical systems and all that are unique versus automotive.
PMY: It’s fascinating that you can use some almost, off-the-shelf Mercury technologies from gasoline powered engines. Wasn’t there a cooling unit—that basically you’re able to use to cool the battery pack or motor?
SH: Yes. Whether gas or electric, the things making torque tend to get hot. There’s a lot of technology already going into this whole E1 series—a lot to focus on. So, we focus on taking one of our current gas engines and taking the internal combustion—what they call the ICE portion—off. Then you can mount the electric motor and the inverter and then the batteries. Those have to be cooled. So if we can find a solution off-the-shelf, it saves us time and development resources.
PMY: Electric motors are known for torque. Do you need a much stronger lower unit on this motor?
SH: We believe we’ve got a good solution. The engine will not be at the max torque all the time. It’s basically going to be higher loaded—more torque when you’re trying to get it up on the foils. But on the foils, you’re really throttling back because you want to save the battery life.
PMY: How about power flow and monitoring? Does it have to be all new?
SH: E1 has a company called Seabird Technologies. Seabird has a pretty cool technical team—they are ex-Formula E (electric automotive racing). So really, we are not involved in that system other than helping with it. They’re using a Formula E ECU—and then that device is really managing the whole control system.
It’s interesting too, because another Brunswick division from the Navico group, the Simrad team, are making the gauges. That’s what’s being displayed to the pilot. And there’s a lot of data coming from that, and that’s being displayed for the television coverage—so the race viewers can see what’s going on. Seabird is really the team that is tying all that together. They’re brilliant guys, and it’s been just a pleasure to work with them.
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This article originally appeared in the February 2023 issue of Power & Motoryacht magazine.