When snowmobile manufacturer Bombardier Inc. introduced the SEA-DOO ® in 1968, the idea of a motor-driven consumer watercraft with no visible propeller was revolutionary. The idea of passengers standing on a watercraft instead of sitting in a conventional hull was also pretty out there. In fact, the design turned out to be too original. Bombardier's new product was not successful, and the company discontinued it in 1970.
A few years later, Kawasaki Motors introduced the JET SKI ® watercraft, which became so popular that many people now refer to all personal watercraft as a jet ski . In the mid-1980s, other manufacturers developed their own Jet ski models, and Bombardier re-introduced its SEADOO design of jet ski.
Since then, demand for personal watercraft has sky-rocketed. There were 1.48 million personal watercraft registered with the U.S. Coast Guard in 2004. About 28.7 million people rode personal watercraft in U.S. waters in the same year
Jet Ski Principle's
A Jet ski moves through the water in the same sort of way a rocket moves through the atmosphere. But instead of using high-pressure gas to generate thrust, the craft uses a jet drive to create a powerful stream of water. In the jet drive, an impeller propels a large amount of water from underneath the Jet Ski through a steering nozzle at the rear of the craft.
The impeller is a rotor-like device that sits inside a cylindrical passageway in the body of the Jt ski. The craft's engine rotates the impeller via a drive shaft. The impeller's curved blades spin rapidly, forcing water up through the passageway and out through the nozzle.
This moves the craft because of the principle described in Isaac Newton's third law of motion. According to Newton's third law, for every action, there is an equal and opposite reaction. In this case, the action is the expulsion of water through the nozzle. The reaction is the movement of the boat or Jet Ski in the opposite direction.
Jet Ski Steering
When you steer the craft, a cable linkage connected to the handles swivels the nozzle at the rear of the craft. This changes the direction of the "equal and opposite reaction." If the nozzle directs the water to the right side of the craft, the rear of the craft pushes to the left. That causes the front of the craft to turn to the right.
Just like a lawn mower or a car, a jet ski or personal watercraft run on two-stroke or four-stroke engines. Two-stroke models have two or three cylinders. Four-stroke models usually have four cylinders.
A noticeable difference between marine and automotive engines is the cooling system. Instead of using a radiator, a marine engine uses the surrounding water to control temperature. Water flows through the engine or through a closed system that includes a chemical coolant.
The Jet Ski engine starts the same way a car engine does. The ignition button, usually found on the handlebars, sends a signal to an electric starting motor. The motor turns the engine to get it started. Then, the engine takes over powering the craft.
Jet Ski Safety features
All newer models of Jet Ski and personal watercraft have a pin or key that inserts into a slot near the ignition. The pin is attached to a lanyard that connects to the operator's life vest or wraps around his or her wrist. The boat will not start or run without the pin in place. If the operator falls overboard, the lanyard pulls the pin out, and the Jet Ski coasts to a stop. This keeps the Jet Ski from traveling very far and reduces the likelihood of a an accident
A trigger on the Jet Ski handlebar controls the throttle, allowing the operator to accelerate. The throttle is as important to steering as it is to acceleration. Without water from the steering nozzle, the Jet Ski cannot change direction.
Instinctively slowing down to avoid an accident is dangerous and can result in a complete loss of steering power. If this happens, the craft will float in a straight line until friction from the surrounding water brings it to a stop. Newer models use a computer to re-start the jet drive if the operator simultaneously releases the throttle and turns the handlebars hard in one direction.
Some Jet Ski models can go in reverse using
a simple shroud that lowers over the steering nozzle. The shroud forces the
water into a U-turn, sending it under the Jet Ski instead of behind it. Since
the rear of the craft always moves in the opposite direction of the flow of
water, this makes the craft go backward. This feature can help get the boat
into and out of the water or get out of tight spaces. It is not designed to
slow or stop a craft that is moving at high speeds.
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