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Jet Ski Evolution
What started as an awkward stand-up turned into a major industry revolution

by Joel Johnson

The "Original" Jet Ski. Say those words to any long-time watercraft enthusiast and they'll know exactly what you're talking about — the Kawasaki Jet Ski 400 — that ungainly stand-up that Kawasaki debuted in 1973 painted the color of pea soup. In fact, most of know the "Original" Jet Ski was the precursor to the modern personal watercraft, the first model successfully sold and marketed in the world.

What few know, however, is that the "Original" Jet Ski was actually two models, neither of which carried the Jet Ski name. The hand-laid fiberglass hulls and decks were built in Japan and the 398 cc twin engines, which were based on Kawasaki snowmobile engines, were fitted with a number of custom-made parts designed specifically for these new fangled "Water Jets."

"It was a long process," said Fred Tunstall, a long-time Kawasaki employee and self-described wrench who worked on the development of the two originals. "And we were working in the dark in a lot of ways. I think most of us who worked on the project knew we had something with the product. Once you spent some time with the machines and got used to riding them, they were a lot of fun and tended to make enthusiasts even of the people working on them.

"But knowing the sport would get this big, that it would all lead to this? I don't think anyone had a idea that would happen."

The Original Idea

The story, of course, begins long before Kawasaki introduced the WSAA and WSAB in 1973. In fact, the idea of a motorized watercraft first hatched in the fertile mind of inventor Clayton Jacobson II in the early 1960s while he was working as a banker.

"I had been racing dirt bikes as a hobby," Jacobson told Personal Watercraft Illustrated (July, 1994), "It was a form of stress relief for me. However, as you know, when you crash a dirt bike, the ground isn't very forgiving. That's why and how I came up with the idea for a personal watercraft. I was looking for a softer landing, and the water offered exactly what I was looking for. Sort of a motorcycle for the water."

Jacobson eventually quit his job as a banker to devote all of his time to developing a personal watercraft, and by 1965, he had built his first running prototype. The craft was a stand-up like those original Jet Skis, but the one-piece hull was made of aluminum and fitted with a fixed, upright handlepole.

A year later, after Jacobson had finished a second prototype, this time using fiberglass, he was contacted by Bombardier Corporation, the makers of Ski-Doo snowmobiles, and asked if he was interested in developing a watercraft for them. The result was the original Sea-Doo, which was manufactured and sold by Bombardier under an exclusive licensing agreement with Jacobson.

However, the Sea-Doo never really caught on. The craft was plagued by mechanical problems, as well as consumer skepticism, and the project was ultimately scraped in 1970.

Jacobson, however, remained undaunted. He continued refining his stand-up model throughout the time he worked with Bombardier, even receiving patents for such things as a pivoting handlepole and a self-righting stand-up craft. However, his licensing agreement prevented him from shopping the craft to any other manufacturers until 1971.

The day after those licensing agreements with Bombardier expired, Jacobson signed a licensing deal with Kawasaki to develop his stand-up watercraft. Jacobson remained more intimately involved in the development of the first Jet Skis than he did with the Sea-Doo, working closely with a number of Kawasaki employees to bring the watercraft to market.

"He could be a handful," said Tunstall. "He was very opinionated and he was sure of what would work and what wouldn't. He wasn't always right, but he was right a good part of the time."

The Birth Of The Jet Ski

Tunstall said that they worked on a half-dozen different prototypes in 1972 before eventually deciding on the two models that would hit the market in 1973 — the WSAA, which used a hull similar to the one found on later 440 and 550 models, and the WSAB, which featured an aggressive, deeper V hull.

"We worked on a lot of different things, but essentially there were probably about six basic prototypes we were testing," he said. "A lot of the stuff we'd try would carry over from model to model, engine stuff and things like that. But essentially there were six concept craft that we built. They were fairly similar to each other, though we'd try different strake patterns or add sponsons, things like that to them to see how they'd respond. It was a lot of trial and error."

At the time, few people in the company knew exactly what to call the craft, let alone who'd they'd be selling them to. Early service manuals referred to them as "Water Jets," while some owners manuals called them "Power Skis."

Even the existence of the two radically different hulls was the result of unanswered questions.

"I think the reason Kawasaki went with the two hulls is we weren't sure who the customer was going to be," Tunstall said. "The flat hull was much more stable and easy to use, but there was some thought that the V-hull would attract riders interested in competition. You never quite knew what it was going to do, especially in rough water, but, man, that thing could carve.The first ride on it, it was worse than a wild horse, but after you spent some time getting used to it, it turned into a lot of fun."

Approximately 550 models were built that first year, a third of them the V hull and the other two-thirds with the flatter WSAA hull.

Other than the hull design, the two models were the same. In fact, the dimensions of the two craft were identical — 6 feet 10 inches long, 24 inches wide and 28 inches high, with a dry weight of 220 pounds and a draft of four inches. That's small compared to even today's stand-ups, but only slightly shorter (2.5 inches) and lighter (about 20 pounds) than the long-lived 440/550 hull.

Unlike later Kawasaki models, the original one-piece hulls were hand-laid fiberglass (which was the main reason they weighed less than later models). They also featured a dull green gelcoat finish with a matching fiberglass hood cover. The bulkheads used wooden braces for added support.

Norm Bigelow, a former test rider who still works at Kawasaki and owns a 1973 WSAB models, said that despite the primitive look of the craft, the quality of the workmanship shines through.

"People may laugh at the pea-soup color, but they really were put together well," Bigelow said. "The 1973 models had a real prototype look to them, with the wooden bulkhead braces, hand-machined hardware and sand-casted aluminum pieces, but the workmanship was very good."

The handlepole was also made of fiberglass, but in two parts, and those parts were in turn riveted together.

"The first prototypes used one-piece aluminum tubes," Tunstall said. "And we switched over to fiberglass on those first models, which worked pretty well. Down the road, when the manufacturing was moved to Lincoln (Nebraska) and we switched to Sheet Molding Compound, we had some problem with the handlepoles breaking and we pretty much shut down production for a year until we got it right."

The engine was based on one Kawasaki used in its now-defunct line of snowmobiles.

"It was a pretty good engine," Tunstall said, "though, even then, most of us knew it was underpowered."

The 398 cc in-line twin featured a bore and stroke of 65 mm by 60 mm and a compression ratio of 5.8:1. Fuel and air were mixed with a single 38 mm Mikuni diaphragm type carburetor, with single piston port intake, pre-mix lubrication and a water-jacketed stainless-steel pipe on the exhaust. The engine was cooled through a hose mounted on the top of the head between the cylinders.

Power was transferred to the water through a 121 mm, single-stage axial flow aluminum jet pump that isn't too far removed from today's pump design. The intake area also was fitted with a casted-in bar scoop, which was based on the same theory as today's top-loader grates. The pump came standard with a three-blade aluminum impeller.

All told, the engine was rated at 26 horsepower at 6,000 rpm and together with the axial flow pump produced 225 pounds of thrust.

"It was enough to get most people up, but if you were above average in size, it could be a struggle," Tunstall said.

The engine compartment added to the prototype look Bigelow talked about. The ignition box was sand-casted, the engine bed was aluminum and all the stainless-steel hardware was hand-machined. The waterbox was made of hand-laid fiberglass. In addition, there were rough spots elsewhere, like the pump attachment bolts which stuck up through the rubber tray mats.

"You could feel those four bolts right through the mat," Bigelow said. "It could make for an uncomfortable ride when you were on your knees.

Still, there were aspects of the craft that were remarkably advanced. The engine, which used aluminum cylinders and stainless-steel hardware, held up to corrosion extremely well.

"They used steel studs on the cylinders and those would occasionally end up rusted together, but that was really it," Tunstall said.

A more difficult problem in the design process was waterproofing the electronics.

"That was the toughest thing we came across," Tunstall said. "Waterproofing the switches and the wiring was a major headache."

It was also the reason for the quirky placement of the switches on the riding tray.

"I think a lot of people look at the location of the switches (which were positioned in front of the tray area along with the choke) and assume it was because so many people started out riding on their knees," Tunstall said. "That wasn't the case. We located them there because that was the easiest place you could keep them dry."

But probably more advanced than anything was the ride, particularly the WSAA.

"The added power on later models helped a lot," Tunstall said, "but the ride on those first 400s was pretty close to what it was on the 440 and 550. I don't think we realized all the things that boat was capable of until it got into the hands of guys like Doug Silverstein or Larry Rippenkroeger or Brian Bendix. Those guys brought out the real potential."

But it was potential that was always there, even from the beginning. Kawasaki may not have know exactly what it had with the Original Jet Skis — heck, they didn't even know what to call them at first — but it was pretty clear they were onto something.

© Copyright 2007 Dominion Enterprises. All rights reserved.


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