The 2008 Sea-Doo RXT-X can hit 68 mph right off the showroom floor, but aftermarket performance kits can unlock the full potential of this high-performance watercraft and push top speed well over 70 mph.

The 2008 Sea-Doo RXT-X can hit 68 mph right off the showroom floor, but aftermarket performance kits can unlock the full potential of this high-performance watercraft and push top speed well over 70 mph.



I was in Orlando last month to test three high-performance watercraft, each a three-seater capable of better than 65 mph. While giving me a download on the new Sea-Doo RXT-X, the media rep for BRP passed along this nugget.

"At boat shows, the first question I get from a potential customer for the RXT-X is how fast will it go," related Tim McKercher of WaterTop Unlimited, which represents Sea-Doo. "And the second question is how fast can you make it go?"

In other words, is there performance left to untap? The answer is emphatically "yes."

In 2000, PWC manufacturers reached a "gentleman's agreement" with the United States Coast Guard, which expressed alarm when PWC speeds topped 60 mph and suggested regulation might be in order. In response, the manufacturers capped top speed at 65 mph with a full fuel load and two passengers in "average" conditions. The fastest boat in our Orlando session, the Sea-Doo RXT-X, reached 68.3 mph with a single rider, which is probably pushing the limit of the Coast Guard's patience.

Acceleration has thus replaced top speed as the focus of PWC performance. That same Sea-Doo zipped from zero to 30 mph in 1.5 seconds, and McKercher explained that the water intake grate used on the RXT-X was designed to promote acceleration at the expense of two to three mph in potential top speed. In other words, Sea-Doo could build it faster, but deliberately slows down the RXT-X.

An RXT-X owner can unlock that potential, however, with a single phone call (or a few mouse clicks) to an aftermarket performance specialist like Riva Racing of Pompano Beach, Fla. The Riva Stage I Kit for the RXT-X will produce a top speed of 73 mph (with one-third tank of fuel) through the application of some fairly simple bolt-on components. Riva offers, or soon will offer, similar kits for the Kawasaki Ultra 250X and the Yamaha FX SHO, and has kits for earlier-model performance PWC.

A key component in the Riva Racing Stage I kit for the Sea-Doo RXT-X is this "top-loader" water intake grate. The vane or foil in the center of the grate feeds water to the top of the impeller, creating a more-even distribution of water to the impeller blades for enhanced efficiency and improved acceleration. Riva makes a similar intake grate for Yamaha and Kawasaki models.

A key component in the Riva Racing Stage I kit for the Sea-Doo RXT-X is this "top-loader" water intake grate. The vane or foil in the center of the grate feeds water to the top of the impeller, creating a more-even distribution of water to the impeller blades for enhanced efficiency and improved acceleration. Riva makes a similar intake grate for Yamaha and Kawasaki models.



The Riva Stage I Kit ($1,170.95) for the RXT-X includes a revised intake tract, a Riva Top Loader intake grate, a Solas Concord impeller, a Riva 2-degree pump wedge, a Riva Pro Series reduction pump nozzle, and a kit to modify the Sea-Doo OPAS off-power steering system. The components in this kit are designed to work together. The revised intake draws air from a cooler part of the engine bay and reduces flow restriction. This supercharged EFI engine will automatically adjust the fuel delivery to match the air volume and density and make more power. The Riva intake grate produces less drag than the stock Sea-Doo grate, and retains a "top loader" design which uses a central vane to direct water flow evenly to the top and bottom of the impeller. This reduces cavitation and increases pump efficiency.

This complete air intake system, part of the Riva Stage I kit for the Sea-Doo RXT-X, replaces the stock airbox. The three-inch diameter intake duct draws cooler air from the nose of the craft through an over-sized K&N filter. Riva Racing says the result is improved acceleration and a 150 to 200 increase in peak rpm.

This complete air intake system, part of the Riva Stage I kit for the Sea-Doo RXT-X, replaces the stock airbox. The three-inch diameter intake duct draws cooler air from the nose of the craft through an over-sized K&N filter. Riva Racing says the result is improved acceleration and a 150 to 200 increase in peak rpm.



The pump wedge trims the nozzle up two degrees, raising the bow and reducing drag for more speed. The pump nozzle outlet is tunable for more acceleration (larger diameter) or top speed (smaller diameter). Note that, with the exception of the intake, this kit does not modify the engine, with means that you should be left with a reliable, stock motor in a boat that simply makes better use of the available horsepower.

Riva says that its sells about 60 percent of it high-performance kits for home installation, while the remainder are sold and installed through Riva-authorized dealers. It will take a pro about three hours to install a Stage I kit. If it's your first time, plan on a half-day if you've got moderate wrenching skills and a basic tool box (plus a special tool from Sea-Doo to remove the impeller).

Want even more speed? Riva is working on a Stage II kit it predicts will take the RXT-X to about 80 mph. That performance will require some engine modification, and a higher degree of mechanical skill to install. Also a high degree of rider skill. So please be careful. And watch out for the Coast Guard.

Editor's Note: Charles Plueddeman is the editor at large for Boating, the nation's largest recreational boating magazine.

Written by: Charles Plueddeman
Charles Plueddeman is Boats.com's outboard, trailer, and PWC expert. He is a former editor at Boating Magazine and contributor to many national publications since 1986.