Pretty geeky engine stuff, yes, but part of the jet drive’s advantage, for sure. Simply put, a jet drive receives more of an engine’s power than sterndrive or outboard powertrains. A stern drive employs two 90-degree transitions and most outboards have one 90-degree transition. Greater efficiency occurs because there are no 90-degree gear-to-gear transitions in a jet drive, which increase parasitic drag. Also, because the impeller is enclosed, that, too focuses the energy, which is why jet drives have such great off-idle acceleration. The stator vane focuses the energy of the thrust. The stator increases the efficiency of the impeller because it removes the “twist” from the water jet created by the impeller. Water is directed out the back of the craft through a stator vane. The submerged impeller spins to create thrust. Water enters the pump cavity on the bottom of the boat. Because the impeller is enclosed, there is also a difference in the shape of their blades. The major difference between them is that an impeller is enclosed inside a pump cavity and a propeller is exposed. Like a propeller, an impeller rotates to move water and create forward thrust. The distinction is subtle because they both perform the same function. How They Work A jet drive uses an impeller rather than a propeller. Given that list of strengths and weaknesses, it’s clear that you will not find a jet drive on a tugboat, where torque and low-speed operation are paramount, but you will find them just about everywhere else. Not good for applications where torque is more important than horsepower.Reverse thrust can act as a braking system.Scalable for applications of nearly any size.One main benefit of a jet drive propulsion system is the absence of propeller blades-making it a much safer system than an inboard or outboard motor. Jet drives are versatile that way, but if you don’t know much about them, let’s break down some of uses where they excel and some where they do not. You will find jet drive propulsion systems on everything from personal watercraft, to family runabouts to giant passenger ferry boats. Here’s a breakdown of their strengths and weaknesses. Jet drives have long had their place in marine propulsion. See all jet drive listings, or read more about Jet Boats in our full-length feature and our Jet Boats explore page.A jet engine uses an impeller rather than a propeller.Some of their strengths include their versatility, their performance in shallow draft applications, and the use of reverse thrust as a braking system however, they do not perform well in low-speed environments. Jet drive propulsion systems are used in everything from personal watercrafts (PWCs) to runabouts and commercial ferry boats.
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