>>>> Yes, I agree and most use electric drive to transfer power to the prop.
 >> 
 >> >     They do? Do you mean outside of submarines?
 >> 
 >> 
 >> You don't have to have mechanical transmissions and if one engine goes 
 >> out, you can run both props from one engine.  Much better control of 
 >> power range too...
>     Dave,
>      Do you have for-sure knowlege of this sort of driveline being used on 
>      surface ships? My information says that most are driven by 
>      mechanically-driven propellors, either from steam turbines or large 
>      Diesels, through reduction gears. Many of the Diesel-powered ships 
>      don't have reverse gears, simply stopping the engine and starting it 
>      again in reverse if there's a need for such action.
Most of the recent large ships are diesel-electric.  Works great since
it allows the diesel to run at constent RPM, you derive ships power
from the same engine ( no need for another engine for the genset ), 
infinite control over the speed and torque delivered to the props, 
when cruising, you can usually shut one engine down and run both props 
from the other engine ( makes periodic maintenence a lot easier too )
One added advantage is that since the engine isn't delivering power 
directly to the prop, the engine/generator assembly can be floated on
shock absorbers - the vibration and noise is significantly less.
The technology has been in place in locomotives for 20 years - it took 
a while to show up on ships but it is proving to save fuel, offer 
better control and be easier to run.
Check any of the commercial marine magazines - Professional Mariner is 
a good place to start - National Fisherman is another one although it 
covers more of the small boats ( too small for these systems to be 
economical )
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