Jet Ski is the brand name of a personal watercraft manufactured by Kawasaki Heavy Industries. The name is sometimes mistakenly used by those unfamiliar with the personal watercraft industry to refer to any type of personal watercraft; however, the name is a valid trademark registered with the United States Patent and Trademark Office, and in many other countries. The term “Jet Ski” (or JetSki, often shortened to “Ski“) is often mis-applied to all personal watercraft with pivoting handlepoles manipulated by a standing rider; these are properly known as Stand-up PWCs. The term is often mistakenly used when referring to WaveRunners, but WaveRunner is actually the name of the Yamaha line of sit-down PWCs, whereas “Jet Ski” refers to the Kawasaki line. Recently, a third type has also appeared, where the driver sits in the seiza position. This type has been pioneered by Silveira Customs with their “Samba“.
In 1929 a one-man standing unit called the “Skiboard” was developed, guided by the operator standing and shifting his weight while holding on to a rope on the front, similar to a powered surfboard. While somewhat popular when it was first introduced in the late 1920s, the 1930s sent it into oblivion.
Clayton Jacobson II is credited with inventing the personal water craft, including both the sit-down and stand-up models.
The two original models were made of hand-laid fibreglass, and included the 1973 WSAA Jet Ski 400, and the WSAB Jet Ski 400. The WSAA featured a flat bottom design that stayed with the JS hull until 1994. The WSAB featured a V-hull that enhanced turning, but was less stable and harder to ride. Only 500 of these WSAB Jet Skis were produced. In 1975, Kawasaki began mass production of the JS400-A, which featured an SMC hull. The JS400 came with a 400 cc two-stroke engine and a hull based upon the previous limited release models.
In 1978, the Jet Ski 440 was introduced. It came with a new jet pump, handlebar mounted ignition controls, and a 440cc two-stroke engine. The 440 engine was almost the same as the old 400, but had a bigger cylinder bore.
In 1982, the Jet Ski 550 became available for purchase. Not only did this new 550 have an engine that generated more power than a 440, with a bigger cylinder bore, and an improved exhaust pipe. The 550 also had a unique “mixed flow” pump that provided better low-end thrust. The 1982 JS 550 was available in yellow, with red decals. The 1983-1989 550s had red hulls, initially with a left front exhaust exit, but replaced by one the right front from 1986 onwards. The 1990-1994 JS 550sx models were white with a rear exit exhaust. This line of JS watercraft maintained very similar designs throughout their production from 1973–1994, and are still the only watercraft to have remained in production for so long.
In 1986, Kawasaki broadened the world of Jet Skis by introducing a one person model with lean-in “sport” style handling and a 650 cc engine, dubbed the Kawasaki X2. Then in 1989, they introduced their first two-passenger “sit-down” model, the Tandem Sport/Dual-Jetters (TS/DJ) with a step-through seating area. Kawasaki began using four-stroke engines in 2003. Combining this with the use of other technologies such as superchargers has allowed some engines to be able to produce up to 260 horsepower (190 kW), as seen in the later Kawasaki Ultra 260X and Sea-Doo RXP, RXT and RXP-X.