History of the Jet Ski - stand-up watercraft


Kawasaki introduced Jet Skis WSAA and WSAB in 1973, the first ever stand-up watercrafts which were limited in production before the company from Akashi decided to bring them in to mass production in 1976.

There are not many out there in the international personal watercraft scene or jet skiing as it used to be in past that know many things about the history of this sport. Actually, many people including enthusiasts of the sport or even Kawasaki CEO’s in many countries who believe that Kawasaki invented the Stand-Up watercraft. Well, they are wrong since there is only one guy in the world who had this vision and drew it on paper and patent it before actually signing an agreement with Kawasaki to produce the first Stand-Up. It was Clayton Jacobson II, an ex banker from Arizona who started working on this project –the project of personal watercraft- in 1960.

On August 15, 1971, Clayton Jacobson’s agreement with Bombardier had expired and it was that very day that Kawasaki signed an agreement to license Jacobson’s invention. By this time, Jacobson had already built his seventh prototype stand-up personal watercraft, using a 372ccRotax water-cooled engine that was in the 1969 model Sea-Doo. However according to Jacobson, Kawasaki was much more receptive and gave him everything he wanted, including corrosion-resistant materials and a 40hp, 400cc, water-cooled engine. The original engine Kawasaki gave Jacobson was a prototype snowmobile engine and it ended up becoming the foundation for 440cc Jet Ski engine.

When Kawasaki manufactured the very first production stand-up personal watercraft, the term or logo of Jet Ski was not yet in use. Originally it was referred as a “Water Jet” on service manuals and later on as “Power Skis” in the owner’s manual.

Jacobson and Kawasaki created six-to-seven different prototypes in 1972, before bringing two models to the market in 1973, the WSAA and the WSAB. The two original models were made of hand-laid fiberglass 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. Approximately 550 of these, WSAA and WSAB, Jet Skies were ever produced, a third of them with the V hull and the other two-thirds with the flatter WSAA hull.

Fred Tunstall, a long time Kawasaki employee had mentioned in the past that they worked on a half-dozen different prototypes in 1972 before eventually deciding on the two models that would hit the market a year later (1973), the WSAA and WSAB. WSAA featured a hull similar to the one installed later on the JS400 and JS550 models. On the other hand WSAB used an aggressive, deeper-V hull. Kawasaki had worked on a lot of different things back in those days but there are probably about six prototypes they were actually testing. The crafts were fairly similar to each other, though Kawasaki were trying different strake patterns or add sponsons, and other things in order to find out how they respond. There was a lot of trial and error involved in to testing back in 1972.

Why the two hull design?
According to Tunstall, Kawasaki went with the two hulls because they were uncertain about who the customer was going to be. The flat hull was much more stable and easy to use; however there was some thought that the V-hull would attract riders interested in competition. Kawasaki never quite knew what they are going to do, especially in rough water. “Man, that thing could curve. The first ride on it, it is worse than a wild horse, but after you spent some time getting used to it, it turned into a lot of fun.”

Apart from the hull design, the two models were the same. In fact, they share the same dimensions, 6-feet, 10 inches long, 24 inches wide and 26 inches high, with a dry weight of 220 lbs and a draft of 4 inches. Those crafts were only slightly shorter approximately by 2.5 inches and lighter about 25 lbs than the long lived Jet Ski 400. The 1973 models had a real prototype look, with the wooden bulkhead braces and hand-machined hardware and sand cast aluminum parts.

The handlepole was also made of fiberglass, but in two parts which were then riveted together. The first prototypes used –one-piece aluminum tubes but Kawasaki switched to the fiberglass on those first models, which worked pretty well. When Kawasaki moved the Jet Ski production line to Lincoln Nebraska, it switched to SMC (Sheet Molding Compound) and then had a few issues with the handlepoles braking therefore, they pretty much shut down production for almost a year until they solved the problem. The aluminum bars when 30? bend and featured a trigger throttle lever.

The first engine
WSAA and WSAB featured the same two-stroke, twin-cylinder water-cooled engine which was actually a Kawasaki snowmobile engine. Engine displacement was 398cc with a bore and stroke of 65 x 60 mm and a compression ratio of 5.8:1. On the inlet side there was 2-1 intake manifold topped with a Mikuni, 38mm diaphragm type carburetor with a piston-port intake system. On the exhaust side, a water-jacketed head pipe was fit with a stainless steel expansion chamber.

Horsepower was translated in to thrust via a single stage axial flow aluminum jet pump of 121.7mm. The pump intake was fitted with a cast-in bar scoop which design was based on the same theory of latter’s top-loader intake grates. The pump featured initially an aluminum two-blade impeller (only a handful of those prototype skis had two-blade props) which was later replaced with a three-blade one.

Both WSAA and WSAB came standard with a trigger throttle lever like many of today’s personal watercrafts. However the start/stop buttons and the manual choke were situated on the dashboard along with the stainless steel hood latch. The reason behind the awkward position of the start/stop buttons was that at the moment this was the safest way to keep the electric box dry. This was actually one the most important aspects that puzzled Kawasaki engineers back in 1972. Many people assumed it was because so many people started out riding on their knees.

Back in 1973 Kawasaki WSAA and WSAB cost $1995 and both craft were the pioneers of Jet Ski that Kawasaki launched in mass production in 1976 with the JS400.

Kawasaki WS-AA and WS-AB
Type: 2T, vertical twin,180? firing piston valve, water-cooled
Displacement (c c ): 398cc
Bore x stroke (mm): 65 x 60
Power (hp/rpm): 26/6.000
Torque (Ft.Lb/rpm): 24/5.000
Compression ratio: 5.8 :1
Fuel induction system: 1 x Mikuni BN38 diaphragm type
Exhaust system: Cast exhaust wet pipe with a 2-1 header
Cooling system: Engine-Exhaust-Open loop system
Fuel consumption (L/h):5.7 @32kph (1.5gal/hr 20mph)
Type: Modified V, double concave (model WSAA-Flat hull); Deep V, Double concave (model WSAB).
Hull material: Hand laid fiberglass, with gellcoat finish and wood bulkhead bracing.
Deck Material: Fiberglass reinforced SMC
Overall length (mm): 2.140 (84in)
Overall width (mm): 610 (24 in)
Overall height (mm): 640 (26 in)
Weight (kg): 110 (243 lbs)
Pump and drive line
Pump: Axial flow, single stage, 6-vane stator.
Pump diameter (mm): 121.7 (4.8in)
Reduction nozzle diameter (mm): 70
Steering nozzle diameter (mm): 84
Impeller: Aluminum, two blade

The Kawasaki Jet Ski stand-up dream started in 1973 and was sadly ended in 2011 with the last model of the stand up jet ski, the SX-R 800. From 1973 to 1976 the JS 400 was the only model ski to cruise the waterways. then in 1977 the JS 440 came about with not too much more power but it was a change. 1982-86 the JS 550 and JS 300 made the scene. the 550 for adults and 300 for the children. once 1987 hit, it was just a steam rolling of new types of jet ski's year after year. Below are the dates and skis that came out within that time period:

1973-1977: 1982-1989: 1990-1995: 1996-2000: 2001-2011:
JS 400 JS 550 550 SX 550 SX SX-R 800
JS 440 JS 300 650 SX 750 SXi Pro X-2 800
650 X-2 750 SX
300 SX 750 SXi
650 SX
JB 650 (jetmate)
JF 650 TS



Fun First!
dallow1 said:
i think what nigel is saying here is that he wants a stand up ski!!!! lovf
clp clp clp Two of them!


Well-Known Member
Maybe Jamie will sell his to old kawa stand ups !!!

Sent from my iPhone using Tapatalk


"The way to a friends home is never far"
Good write up Nigel clp
I was always aware that Kawasaki were first on the scene with Jet-ski's, however is it true that Kawasaki has patented the name "Jetski" and other companies can only refer to their product as PWC"s rjs2

Cheers br



The next obvious step was to sit downs..

The first multi-seat JetSki was the 1986 X2, a hybrid two person craft with the novel ability to operate in either stand up or sit down mode. Both styles of machine proved immensely popular and the lakes and seaside towns of America and Europe soon played host to a new form of recreational watercraft offering the performance of a speed boat small enough to be stored in a normal domestic garage and light enough to be easily and launched and recovered or towed behind a family car.

In terms of the evolution of the Jet Ski product, solo skis were increasingly seen as the preserve of the expert or dedicated racing owner while the multi-seat craft became the obvious route for developing the Jet Ski product line for the whole family to use allied to desire for extra storage and creature comforts. Of course being such a popular hobby craft in America, it was obvious that performance and excitement had to be retained by the next range of products but so too was refinement.

Given Kawasaki’s notoriety in the field of three cylinder, two-stroke engines, it was wholly fitting that the following generation utilised water-cooled units with the cylinders running front to back starting initially at 900cc in 1995 and evolving the very next year all the way to the powerful 1100cc ZXI.

Using normal engine technology, there was only so far that two-stroke performance could be pushed in light of noise, exhaust emissions and fuel consumption.

Taking the power unit from the road-going ZX-12R, the team at KHI “marinised” the engine and fitted the fuel injected motor into a race-developed hull christening the impressive 250 horsepower personal water-craft (PWC) the Ultra 250X.

Eventually enlarging the Ultra’s engine to 1500cc released more power and torque but, for many, that was not enough, they demanded more than conventional tuning could deliver. With a turbocharger considered, this technology was eventually rejected in favour of supercharging.

The result was an increase to first 260 horsepower and, more recently, a twin vane Roots style supercharger, delivering a considerable 310 horsepower via the Ultra 310 series.



International Day of the jet ski.

On August 15, 1971, Clayton Jacobson’s agreement with Bombardier had expired and it was that very day that Kawasaki signed an agreement to license Jacobson’s invention.



"The way to a friends home is never far"
Thanks Nigel wh

We will eventually rule the waves, so the world can be a better place rjs2



Jetskiers. Species evolved.
cl that vid at the top is a classic! had to watch it twice sk. see the dood going to the beach in one of the coolest classic cars of all time (early '70s el camino ute) jetski in the back, all set for a day on the water, wearing his suit and shiney leather shoes. ag we've all come along way since then. jetskiers evolve faster than normal humans, thank god the jetskis and fashion sense has been able to keep up with us