How do jet boats work?
A jet boat also often called a wave runner or jet ski is a type of personal watercraft that is propelled by water ejected from the back of the craft. Water is pulled into a pump-jet and sprayed out of a nozzle in the rear or stern.
Historically, motorized boats are powered via a propeller that sits in the rear of the craft below the water line. The propeller turns, basically, turning the water away from the boat like a screw. This pushed the boat forward or backward depending on the direction of the propeller. Imagine a screwing a bolt into wood that pulls the screw.
The obvious downside of a submerged propeller means that propeller craft can be damaged by shallows and unseen rocks below.
A jet ski was designed to get around this issue. Jet boats use a pump-jet or a series of pumps to pull water into the craft from the underside of the front then expel it through a nozzle at the rear or stern. Most jet boats are designed to spray the water via the nozzle above the waterline and not below. This spray or thrust pushed the watercraft away from the jets by expelling water.
According to Wikipedia, “Jet boats were originally designed by Sir William Hamilton (who developed a waterjet in 1954) for operation in the fast-flowing and shallow rivers of New Zealand, specifically to overcome the problem of propellers striking rocks in such waters.”
