We have all travelled on high speed ferries but why do they use water jets as their means of propulsion? The answer is simple: economy if you intend to travel through the water at greater than 20knots water jet drive is more efficient and so cheaper to run than a propeller system so more profit for the ferry companies. Economy is also a consideration for most leisure boaters but in today’s the world of family motor boating the water jet drive has so much more to offer.
Unrivalled manoeuvrability, marinas are squeezing as many berths into their over priced waterfront sites as they deem practical. The ability to turn through 360 degrees around the boat’s centre point and maintain precise positioning at low speeds is becoming essential.
Versatility, with nothing protruding below the hull you can take water jet boats to places no propeller boat would consider. In New Zealand, home of the modern jet boat’s inventor Sir William Hamilton, they race jet boats in 3” of water! So exploring the upper reaches of estuaries and anchoring off the beach is never a problem.
Safety, no rotating parts outside the hull mean less chance of doing damage to sea life or swimmers. It is this quality combined with manoeuvrability and safe access to the shallows that makes the water jet the drive of choice for inshore rescue boats.
Security, popular cruising grounds are tragically awash with all sorts of flotsam from legitimately laid fisherman’s floats to highly dangerous polypropylene cargo nets accidentally washed off the decks of commercial shipping. A fast propeller driven motor boat can be left disabled or damaged by all sorts of waterborne rubbish that a jet boat will skim over unaffected.
Simplicity, in the potentially hazardous environment that we make our playground simplicity equals safety. Fewer external moving parts mean less to go wrong. In basic terms water jet drive is an engine directly coupled to a powerful water pump. The water pump is entirely within the hull and has access from above the waterline so if you are unfortunate enough to draw anything into your drive you can switch the engine off, roll your sleeve up, reach in and pull it out, that has got to be better than putting a wetsuit on and diving into cold water with the breadknife!
Combine simplicity, security, safety, versatility and manoeuvrability with the economy of efficiency and it is not surprising that nearly half the Swordsman Marine boats built were fitted with water jet drive. For classic lines with practical technology take a look at the Swordsman 30. Test sails out of Hamble Point Marina.