The mid-sized performance watercraft market has been strictly dominated by Yamaha and Sea-Doo. No other manufacturer offers a watercraft to directly compete with Yamaha’s GP1800R SVHO or Sea-Doo’s RXP-X 300. While Kawasaki does offer the highest horsepower machine money can buy, the Ultra 310 series, it’s hefty size and weight prevents it from competing alongside the best of what Yamaha and Sea-Doo has to offer.
However, Kawasaki does have a fantastic mid-sized watercraft; the Kawasaki STX line of watercraft would be an excellent starting point for the next big high performance ski if it only boasted the 310 horsepower supercharged engine found in it’s big brother. Most recently, Kspeed Performance has published a video showing off their STX310LX conversion ski and covering exactly what entailed fitting the supercharged engine into the STX hull. Last year the Watercraft Journal was fortunate enough to ride the STX310LX; you’ll want to read the full story here.
Kspeed’s STX310LX is a fully functioning watercraft with electric trim, stereo system, and a display from a 2019 Ultra 310. Surprisingly enough, this conversion was built with almost all original Kawasaki manufactured parts. With only modifications needing to be made to the pump shoe, airbox bracket, and intake hoses, this is otherwise a bolt-on installation when utilizing original parts dating back to the Ultra 250. The result is a lightweight, nimble, and 80mph-capable watercraft out of the box.
Kspeed’s creation is not, by any means, an engineering marvel; an individual with any form of mechanical skill can build their own STX310 in their home garage. Being that it is such a simple conversion, thanks to the utilization of almost all factory parts, hopefully Kawasaki will take the hint and offer the STX310 to the masses! If and when the day comes, Yamaha and SeaDoo will certainly have a new competitor on the buoy course!