Maybe you'll change your mind after reading the below ...
From US DOD DSTC - Section 13: Marine Systems Technology
Cavitation tends to degrade the performance of conventional fully
wetted (submerged) propellers at speeds above 30 to 35 knots.
The waterjet is a different type of propulsor. As an alternative
for countering propeller cavitation problems for high-speed craft
and special-purpose craft, the waterjet, which is driven by a gas
turbine, provides a jet-reactive thrust of high-velocity water
expelled through a nozzle. With a speed range above 45 knots,
waterjets, whose principal advantage is improvement of vehicle
maneuverability over the whole speed range, are typically applied
to patrol boats, surface effect ships, hydrofoils, and motor
yachts. Kamewa waterjets have been installed on more than 500 craft
since the early 1980s. Experience of these units is reported by
Kamewa to demonstrate other operational benefits (Croner,
1997):
- Good fuel economy. Above 2025 knots usually competitive with
propeller propulsion for the actual types of craft;
- Reduced internal noise and vibration levels compared to propeller
propulsion. Noise reduction usually 710 dBA;
- Reduced hydroacoustic noise, usually about 10 dBA;
- Power absorption at constant rpm is insensitive to the ships
speed;
- Diesel engines are not over torqued or over speeded;
- Reduced engine wear;
- Cruising units can be used at full power during cruising as well
as at top speed together with booster unit;
- Shallow draught and protected installation; and
- Well proven, reliable design.
