The basic reason is plumbing. Thrusters have to push a large volume of
water at fairly high speed and low pressure. That cause a lot of
friction in pipes and consequent energy loss. Hydraulic systems push a
relatively small amount of fluid at moderate speed and very high
pressure. You can push it through smaller pipes over longer distances
with less loss of energy.

Much more efficient to push the water through a very short length of
pipe and send the energy from the engine to the thruster with hydraulics.

Ron Thornton wrote:
Jim Woodward's comment on hydraulic bow thrusters resurrected a thought
I had a long time ago and never followed up on. If you are going to pump
a fluid, why not pump seawater to nozzles in the hull for thrust.

Regards, Ron


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
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