The Sialia 57: An Electric Boat With No Compromises?

Think electric boat and odds are you’ll envision a catamaran covered stem to stern with solar panels, or a boat flying on foils.

But the Sialia 57 Deep Silence doesn’t fit those descriptions. It looks more like a sleek Northern European weekend yacht, and it’s propelled by electric motors, batteries and a range extender. “We wanted a boat that goes fast and far on batteries. The idea is not to get compared to a normal electric boat, but to get compared to a boat, full stop,” says Sialia co-founder Tomasz Gackoski, an aerospace engineer. “It’s an electric boat with no compromises.”

The two-stateroom 57 has all the bells and whistles you’d expect on any internal combustion-powered luxury yacht. The boat is the brainchild of Polish entrepreneur and Sialia CEO Stanislav Szadkowski, who did not skimp on this proof-of-concept boat with superyacht-quality finishes. It was designed in collaboration with Netherlands-based Denis Popov, who focuses on lightweight naval design, and Vripack, the Dutch naval architecture firm.

The boat was built in Latvia, and debuted at the 2024 Fort Lauderdale International Boat Show, where we were able to tour it. We also asked the company principals how the 57 is able to go “fast and far” on electric power.

As Gackoski explained, it starts with a super lightweight, nearly 100 percent carbon vessel with a long, narrow, slippery hull. Using carbon instead of fiberglass creates a huge weight savings, which helps offset the heft of the batteries and makes for a more efficient hull. The lighter the boat, the less horsepower you need. “I think there are maybe 3 or 4 pieces that are stainless steel, one of which is the shower,” he said, pointing out that even that was supposed to be made of carbon.

The propulsion system comes from Ampros, a company Szadkowski and Gackoski founded to supply electric propulsion solutions for Sialia and other builders. Szadkowski has a master’s degree in mechanical engineering and decades of experience with heavy-duty batteries. Ampros supplies a soup-to-nuts system solution. That means software and hardware. The hardware includes 256 kWh of heavy-duty batteries that use a lithium nickel manganese cobalt oxide chemistry, which gives high energy density and operating voltage. The batteries are organized in three strings to provide redundancy (two strings can fail and the third will still provide power). The batteries feed the twin 400-kW electric motors that have a peak of 500 kW (equivalent to almost 1,350-hp total). Propulsion is delivered via straight shafts. At 6 knots, the batteries provide a range of about 100 miles. When the batteries get low, the range extender fires up.

That range extender is a diesel engine of Ampros’ own design, built on a biofuel-capable FPT (Fiat Powertrain Technologies) block, selected for its light weight. The range extender can recharge the batteries in half an hour, using 13 gallons of diesel from a 396-gallon tank. Once the range extender has made enough juice, you will travel in silence on electric motors only. Everything is controlled seamlessly by a proprietary ship management system. Gackoski showed how battery levels, energy consumption and everything else on the boat can be monitored on one of the two enormous Garmin multifunction displays at the helm. Cruise speed is between 15 and 17 knots and top speed is about 25 knots. With a full battery and a full fuel tank, the boat has a range of 300 miles while doing 16 knots.

Szadkowski and Gackoski believe that electric propulsion, besides running quietly and without exhaust, comes with many other upsides. Electric motors have much better torque, provide faster acceleration, get a boat on plane faster, are reliable and durable. “Electric motors are rated for 30,000 hours,” Gackoski said, adding that, unlike internal combustion engines, they hardly need any maintenance.

To prove the 57 could go fast and far, they took it for a romp from Barcelona to Monaco. The Sialia covered the 264 miles in one go, running at 16 knots, although swell forced her to slow to 9 knots for a spell, but she still averaged 14 knots overall.

Some people might call the Sialia a hybrid, but she’s not. The FTP diesel is not connected to the props. The props and shafts are turned by the electric motors, which are powered by electricity from the batteries. The batteries are then recharged by the range extender or shore power. The shore power can come from almost almost anything: a 50-amp marina connection, a 100-amp pedestal, or a fast DC charger (the boat has a CCS connection).

The 57 is a one-off and meant to be a proof-of-concept boat. “We’ve done this one, so we can go around the world and show everybody that it makes sense,” Gackoski said. The relatively small 256-kWh battery was chosen because it can be recharged overnight by the 50-amp power supplies found at most marinas. “It doesn’t make sense for us to put more batteries in if you cannot charge them overnight,” he said.

Future 57 builds will be extended by two feet to become the Sialia 59, which will have more options, including larger batteries and faster charging capabilities, including for those who have fast chargers for their electric cars. “Some people, they have a nice villa, and as much power as they want. And for them, there is a 700-kWh battery,” Gackoski said.

The company has other models in the works. The first all-carbon electric Sialia 45 Sport is being built in Poland. Gackoski says that boat is currently on target to make a world debut in Cannes in September and a U.S debut at FLIBS 2025.

Szadowski and Gackoski’s goal is to make the range extender unnecessary, but they know it will take time for the battery technology to develop.

“For the next 5, 10, 15 years, the range extender will be needed,” Gackoski said. “But it’s more about how you use the boat. If you’re doing 90 percent of your time on the [ICW] and you’re going 6 knots, with this boat, you can do over 100 miles. If you go to Bimini with the range extender, which is probably one of the fastest chargers on the planet, we can recharge this boat in less than half an hour.

“We are so sure about the whole system that we give a five-year warranty on everything. Except for the diesel engines,” he added laughing, “because we don’t trust them. 

February 2025