WHETHER YOU’RE LOOKING FOR A SOLAS, UTILITY RIB OR A LIMOUSINE, YOU SHOULD CONSIDER THE JET OPTIONS AVAILABLE. MANOEUVRABILITY, SHALLOW DRAFT AND OVERALL SAFETY ARE JUST THREE OF THE MAIN ADVANTAGES
We can thank a young engineer from New Zealand for producing the world’s first commercially successful marine jet engine. In 1954 William Hamilton was asked to design a vessel to cope with the shallow fast-flowing rivers around Christchurch.
He investigated the American Hanley Hydro-Jet, a model which drew in water and fired it out through a steerable nozzle underneath the boat. Even when further adapted it did not work well. A colleague suggested moving the nozzle to just above the waterline. Throughout the late 50s and early 60s Hamilton continued to develop the successful business which is now known as Hamilton Jet and Hamilton Marine. However, when asked how he came up with the idea Bill Hamilton said, “I do not claim to have invented marine jet propulsion. The honour belongs to a gentleman named Archimedes, who lived some years ago. I simply refined the design.”
Waterjet propulsion has many advantages over other forms of marine propulsion, such as stern drives, outboard motors, shafted propellers and surface drives. These advantages include reliability as the waterjets have fewer moving parts and most major components inboard, minimising the chance of accidental damage and increasing the life of components. The engines give the boats excellent manoeuvrability and precise steering control at any speed. With a zero speed steering effect providing 360° thrusting ability for docking and holding stationary. The engines tend to deliver excellent speed (dependent on the vessel) with the waterjets designed to be optimised for speeds from 25-50 knots, dependent on application’s engineering variables including hull resistance and type, engine power rating and rpm, impeller rating, etc.
The drive units are highly efficient with propulsive coefficients as good or higher than the best propeller systems achievable at medium to high planing speeds, and by their very nature cause less drag and have a shallow draught with the absence of underwater appendages and propellers reducing hull resistance. In a shallow draught – the waterjet intake is flush with the hull bottom to allow access to shallow water areas and beach landings with no risk of damage to the drive.
The engines on the whole tend to have little downtime and simple maintenance routines are smooth, quiet and give little hull vibration, no torque effect and no high speed cavitation giving maximum comfort levels on board.
The jet engines offer more safety for people and other marine life in the water around the boat. The engines are simplicity personified with a single packaged module with no heavy and expensive gearbox required for many installations. It’s simply a driveline from engine to jet coupling.
More tender brands are getting on board with jet engines and with some serious developments in marine diesel outboards, Yanmar are one company who are developing some great new diesel jet packages with Williams.