Learning Curve for Waterjets

Visit the Web sites of some waterjet manufacturers or glance at their brochures and you find a lot of information on how waterjets work and their best applications — more information than is usually available in propeller brochures.

That’s because a lot of people don’t understand waterjets. When things go wrong it’s often because a waterjet best suited for pleasure boat use is put into a workboat application. “Pleasure boats want speed. They are not carrying variable loads,” said Graham Scott, president of Ultra Dynamics in Columbus, Ohio, and builder of the UltraJet. 

Scott said that these waterjets tend to cavitate when there’s a load, and it becomes hard to turn the engine’s power into thrust. “People have to crank the throttle higher. They often don’t get more speed, and they walk away thinking ‘jet drives are no good in a workboat.’ ”

Instead it’s just a case of the wrong waterjet for the application. “It’s important that the selection of a jet be based on a boat’s mission, the type of hull, power and displacement,” Scott said. 

In fact, he sees much of his role in marketing the UltraJet as educating potential customers. And Ultra Dynamics has one of the most informative Web sites (www.ultradynamics.com) to accomplish the task. 

There’s information on when waterjet drives should be used, boat design considerations for waterjets, and frequently asked questions.            M. Crowley 


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