I was a commercial
fisherman and used hydraulics every day. It's a great way to transmit power, but sucks up a lot of HP. Pumps, motors, hoses, valves and seals
all have a life span that is shorter than the average transmission
. Permanent installations are plumbed in steel
pipe. And even steel
pipe can only go thru so many pressure changes. It flexes every time it takes up pressure, eventually becoming fatigued.
I also owned diesel electric
tugs and that would be my preferred system for non-direct drive. But it has losses, too and is expensive.
had about 200hp engines. A single
50 hp diesel
is going to push it at a little over hull speed
. Maybe 8-9 knots.