Kawasaki extended its high-performance domination into the realm of personal watercraft with the 250 horsepower 2008 Jet Ski Ultra 250X. The quickest and most powerful production PWC in history, Kawasaki’s supercharged Ultra 250X tears across the water at an electrifying pace that will invigorate even the most jaded of speed enthusiasts.
The 2008 Ultra 250X’s engine, jet drive and hull incorporate racing technology refined through Kawasaki’s multiple IJSBA championships. This knowledge application allows it to deliver the awesome acceleration of a drag racer, and help ensure excellent hook-up even in rough water.
With a 1,498cc engine derived from Kawasaki’s capable Jet Ski STX-15F watercraft as the foundation, the Ultra 250X produces power comparable to a normally aspirated high-performance three-liter engine. It accomplishes this amazing feat via the addition of a Roots-type supercharger. Unlike centrifugal superchargers or turbochargers, the Ultra 250X’s high-volume direct-drive supercharger delivers boost virtually instantly at any engine speed from idle to redline. This produces a linear, smooth torque curve that is ideal for a personal watercraft that needs to accelerate hard all the way from a standstill to its breath-taking top-end speed.
2008 Ultra 250X
Heat build-up from compressing the intake air is a common drawback of forced-induction. The Ultra 250X uses of a large-capacity intercooler to overcome this handicap. With the 250X’s supercharger compressing the air to a maximum boost pressure of 11.4psi, the intake charge can reach extremely-high temperatures potentially limiting the engine’s power output. However, the 250X’s large-capacity intercooler brings the pressurized air down to ambient temperature or even less –ideal for producing maximum power.
A huge 155mm jet pump featuring the largest PWC impeller and nozzle Kawasaki has ever produced transfers the big power from supercharged 1,498cc engine into the Jet Ski Ultra 250X’s blazing acceleration. Developed based on lessons learned from Kawasaki’s race machines, this pump was designed to deliver predictable thrust and good “traction,” even in rough water.
A significant factor in this extra “traction” are the pump’s eight guide vanes that smooth the flow of water from the impeller for efficient and powerful propulsion. The pump also incorporates a groove from the center to the rear of the ride plate which makes it easier to hold a stable heading for straight line riding. Complimenting the 155mm jet pump is an equally large, sophisticated three-blade impeller that delivers high performance with smooth and quiet operation.
2008 Ultra 250X
Once up to speed, Kawasaki’s Ultra 250X precise handling and superb stability are equally impressive, thanks to a hull specifically designed to capitalize on the engine’s awesome performance.
In addition to more power and acceleration than any other production watercraft on the planet, the Ultra 250X also boasts a race-developed hull. Its hull design is just as comfortable in rough conditions as in calm. Even at high speeds, rough water can do little to deter the Ultra 250X. This combination of unearthly power mated with the latest hull technology permits Kawasaki’s flagship to literally cleave through waves that would send lesser machines ricocheting to a safe harbor.
Thanks to a specifically engineered hull, the Ultra 250X has the precise handling and superb stability to match its acceleration and top-speed capabilities. A fiberglass reinforced plastic (FRP) hull includes carefully designed sponsons and chins for enhanced straight-line stability and precise cornering, combined with a 22.5 degrees deep-V hull that leans into corners like a motorcycle. This provides a smoother ride in rough water, helps passengers keep the rider in control during peak cornering g-forces.
2008 Ultra 250X
The Ultra 250X features a five-step adjustable handlebar position that allows either stand-up or sit-down riding for a wide range of riders to enjoy superior comfort and versatility. As Kawasaki’s flagship watercraft, the 250X includes thoughtful standard features like an enormous 53 gallon of storage space including a detachable front storage compartment and a 20.6 gallon fuel tank for substantial cruising range.
From horsepower to handling and everything in between, once the spray settles after the first ride, one thing will be certain. This powerful “ultra” 2008 Kawasaki Jet Ski Ultra 250X model delivers a level of performance and excitement that is unmatched by any other watercraft.
Supercharged and intercooled, 1,498cc, liquid-cooled in-line four-cylinder engine
Compression ratio is 7.8:1 to minimize detonation at high-boost pressures
Inconel exhaust valves are fitted for superior heat resistance and enhanced reliability
33.4mm intake and 28.3mm exhaust valves
Precise power adjustments are easy with a throttle lever that is designed to prevent finger fatigue on longer rides
2008 Ultra 250X
Roots Type Supercharger
Force-feeds the engine two liters of air with every revolution, providing a stable supply of high-pressure intake air at all rpm
Produces large amounts of boost even at low rpm, for instant and powerful acceleration right off of idle
Provides a very flat and meaty torque curve with step-free power across the entire rev range without any of the lag associated with turbochargers
Produces more low RPM boost than competitive or aftermarket systems with a maximum of 11.4psi of boost pressure
Two different air bypass valves are used to prevent over boosting at low and medium rpm
The smaller air bypass valve releases low amounts of excess pressure build-up, for precise boost management
The larger air bypass valve is used when excessive boost pressure is accumulated, to maintain an even intake pressure even when giving full-throttle from idle
Efficiently cools the high-pressure intake air
Cooler air results in higher combustion efficiency and high engine output
Liquid-cooling allows the intercooler to maintain consistent thermal performance
High-flow fuel injectors with four orifices are fitted to complement the increased power output and improve combustion efficiency
Single throttle body features a large 60mm bore diameter
2008 Ultra 250X
4-into-2-into-1 powerboat-style exhaust system, which routes the exhaust pipe upwards.
Allows the smoothest path for exhaust gases, maximizing exhaust efficiency
Efficiently converts the Ultra 250X’s massive horsepower into thrust using a large-diameter 155mm jet pump
Developed based on feedback from Kawasaki’s race machines, this pump was specially designed to deliver stable output and good “bite,” even when riding on rough water
Reverse lever has been moved from the right side to the left side for easier operation
The large, sophisticated three-blade impeller delivers both improved thrust in the higher speed ranges and high performance and quiet operation
An eight-vane intake guide is used to smooth and regulate the flow of water from the impeller for efficient and powerful propulsion
Features a groove from the center to the rear of the ride plate, to enhance straight-line stability
2008 Ultra 250X
Feedback from Kawasaki’s IJSBA championship winning racing machines integrated into design
Specially designed to cope with the engine’s horsepower
Offers a combination of high stability and responsive handling in both calm and rough-water conditions
Delivers the neutral handling and turning characteristics that made Kawasaki JET SKI watercraft famous
The lower hull is specially designed to distribute the engine and power delivery loads over a wide area
Although it has a similar V-shape to the JET SKI STX-15F, the Ultra 250X’s hull enables a high bank angle, for motorcycle-like turning performance. This reduces the side G-loads imposed on riders during turns
The 22.5° V-angle at the bottom of the hull helps prevent spinouts during sharp turns and to provide a smoother ride in rough water
Bottom of the hull slants upwards steeply from the center section to the bow, so the Ultra 250X can penetrate swells and waves with less shock; delivering extreme stability at low speeds and pushing through waves rather than bouncing over them at high speeds
Battery located inside the front storage area near the center of the machine, avoiding concentrating heavy components at the rear and freeing up space inside the engine bay
Integrated sponsons extend from the hull, providing stable wallow-free straight-line performance and contributing significantly to the 250X’s excellent high speed maneuverability while helping to retain the narrow hull design
The Ultra 250X’s Kawasaki Splash Deflector uses three bottom mounted ridges and an additional deflector mounted at the top to deflect water splashing forward from under the hull
Whether turning or blasting straight ahead, at high speeds or low, the Quattro KSD minimize spray, allowing greater rider concentration
2008 Ultra 250X
Kawasaki Smart Steering®/SLO-Mode
Kawasaki Smart Steering® (KSS®) monitors steering input and engine speed and, when certain conditions are met, raises rpm to initiate a desired turn, helping new riders better enjoy the performance of this remarkable machine
Smart Learning Operation (SLO) allows newer riders to become familiar with the handling and response of this JET SKI watercraft at a more relaxed pace before unleashing the full performance of the Ultra LX
Two separate keys, one for SLO-mode and one for full-power operation help prevent confusion over which setting is in use
Comfort and Convenience
Five-way adjustable handlebars allow operation while standing or sitting and suit a wide range of riders
Relatively narrow seat is comfortable whether riding stand-up, seated or with passengers
Ergonomic deck design gives plenty of legroom
A long rear boarding step makes it easy to climb onboard, and the step retracts inside the bumper to prevent damage
A quick and easy under hood hose connection allows an easy method to flush sea water out of the engine
Mirrors are mounted to the upper deck to facilitate opening of the hatch cover
The large-capacity, fully sealed 53-gallon storage area with a detachable storage tray has plenty of room for recreational equipment
Mounted on the center console is a detachable drink holder with space for two drink bottles
Ideal for small items, a compact storage area is integrated with the under-seat rear grip
Big Fuel Capacity
20.6 gallon fuel tank has more fuel capacity than any machine in its class