On Sun, 11 Nov 2007 07:02:43 -0500, "Eisboch"
wrote:

And diesel/electric submarines are pretty damn efficient.

If the setup allows the diesel engine to run at a constant, optimum RPM,
regardless of vehicle speed (as diesels are really designed to do) there
will be a gain in efficiency.

Yes, and that's important on a train, it's likely having a
continuously variable transmission that allows the engine to run at an
efficient speed regardless of the actual load. On a boat running at a
more or less constant cruising speed, running at the right RPM is a
function of reduction gear ratios and prop pitch. Once you get those
two factors set correctly they will stay that way in most cases. The
one exception that comes to mind is slowing down for rough seas but
real men in real boats don't do that do they? :-)