The roar of this weekend’s Seafair hydroplane races on Lake Washington reawakens a six-decade-old Seattle tradition – but it also heralds changes for a sport that’s been compared to NASCAR on water.

Seattle has been a hot spot for hydros since 1950, when a made-in-Seattle thunderboat called Slo-Mo-Shun IV set a world speed record on Lake Washington and brought the nation’s premier unlimited hydroplane race to Seattle the next year.

Today, the restored wood-and-metal boat rests in Seattle’s Museum of History and Industry. Its builder, Stan Sayres, would probably still recognize the streamlined, souped-up vessels that venture forth from Stan Sayres Memorial Park. But he wouldn’t recognize the technology under the hood.

“It’s quite a bit of difference in the boats, the engines,” said Tom Thompson, driver of the Miss DiJulio/J&D’s U-11.

Like racecars and airplanes, the boats that are built today incorporate carbon-fiber composites to reduce weight and increase speed.

“We’re probably, depending on the size of the boat, between 20 and 30 miles per hour faster than we were before,” Thompson said. “A lot of that has to do with the new technology and the design of the hull, as well as the material that’s used to make it lighter.”

Miss DiJulio’s owner, Shannon Raney, said the boats are also a lot more instrumented than they used to be. An electronic system for data logging and telemetry, built by British-based Cosworth and installed in the boat’s cockpit, monitors speed, engine temperature and even how far Thompson is pressing down the pedal.

“It keeps track of every single thing that happens in the race while it’s out there running, and he’s got a digital screen in front of him … that tells him everything that’s going on as well,” Raney said.

The heart of a hydro is the engine, and on that front, change is coming more slowly.

Hydroplane racing took off in the U.S. just after World War II, when surplus airplane engines became available for a song.

“A few hundred dollars bought you an engine,” said Doug Brown, a member of the crew for the Miss Wahoo thunderboat. “Nowadays you’d be lucky to find one of these engines for $100,000. … The golden age of hydroplanes really showed up with the World War II engines.”

Some of the boats racing this weekend, such as Miss Wahoo and Oh Boy! Oberto, still use turbocharged Allison V-1710 aircraft engines that are lovingly maintained by Brown and other veterans affiliated with the Hydroplane and Raceboat Museum in Kent, Wash.

The museum and its volunteers “keep the thunder in the thunderboats,” Brown said.

Boats built on more modern designs rely on surplus Lycoming T-55 turboshaft engines that were built for CH-47 Chinook helicopters. Those engines are lighter and somewhat more available, but only so many were made.

“They’ve got to find some other new source of power, because they’ve run out of the turbines,” Bill Wester, who’s on the crew for the Oh Boy! Oberto. “You can still get ’em … you buy one for $100,000 and spend $100,000 to get it rebuilt.”

Even that estimate may be too low. Another member of the pit crew chimed in that if you want to win rather than finishing in sixth place, the cost for a new engine is more like $450,000 to $500,000. Engineers are developing V-12 engines designed specifically for hydroplane racing, such as the Aardema V1200, but those engines are still in the prototype stage.

The technology for propellers is also advancing, thanks to computer-guided, five-axis metal cutters. “Propellers are always the secret weapon,” Wester said. But high-tech propellers don’t come cheap: The price can run upwards of $15,000.

“It’s a rich man’s sport nowadays,” Brown said.

The way Brown sees it, there are four boats that have the best technology, and the best chance of winning the top prize: the U-1 Miss Homestreet, the U-9 Les Schwab Tires, the U-12 Graham Trucking and the U-16 Oh Boy! Oberto. Brown rates the U-11 Miss DiJulio/J&D’s as an up-and-comer, thanks in part to its technology.

Another piece of the technology has to do with how people see the races. People still crowd in to see the race from the grandstands at Sayres Memorial Park, or from the scores of boats tied up to the traditional log boom set up in Lake Washington. But TV ratings have declined to the point that, starting this year, the Seafair races will no longer be aired live on television.

Instead, the KIRO7.com website will be live-streaming a camera view during Sunday’s big finals, and KIRO TV will broadcast a 90-minute wrapup show at 6:30 p.m. that evening.

Streaming video could well be the future for experiencing the thunderboats: A stealthy startup called Immersion Networks is conducting an experiment this weekend to document the hydroplane races and the Blue Angels air show in virtual reality, using a Z-CAM S1 VR camera and an innovative audio recording system.

“This is the future of how you’re going to be seeing and hearing things like Seafair,” the company’s founder, Paul Hubert, said as he set up the equipment.

Can high tech breathe new life into Seattle’s hydro traditions? Tom Thompson, who’s been in the boat racing business for more than 30 years, says it already has.

“The old days, they were fun,” he said. “But right now what we’re doing is a whole lot more fun.”

An earlier version of this report incorrectly referred to Immersion Networks as “Immersive Networks.”