On Sun, 11 Nov 2007 21:39:44 GMT, Short Wave Sportfishing
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? :-)

So why wouldn't it work on a larger boat?

It will work but there is little or nothing to gain unless the boat
runs at a variety of different speeds and/or the engines exceed the
ability of reasonably sized mechanical transmissions. Diesel-Electric
is considerably more expensive than a mechanical transmission and is
not cost effective in boats with less than locomotive sized engines.

On Sun, 11 Nov 2007 17:14:19 -0500, Wayne.B
wrote:

On Sun, 11 Nov 2007 21:39:44 GMT, Short Wave Sportfishing
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? :-)

So why wouldn't it work on a larger boat?

It will work but there is little or nothing to gain unless the boat
runs at a variety of different speeds and/or the engines exceed the
ability of reasonably sized mechanical transmissions. Diesel-Electric
is considerably more expensive than a mechanical transmission and is
not cost effective in boats with less than locomotive sized engines.

Ok - so if Navistar can make this work for utility lift trucks with
that kind of efficiency, would they work in boats?

On Sun, 11 Nov 2007 22:37:31 GMT, Short Wave Sportfishing
wrote:

It will work but there is little or nothing to gain unless the boat
runs at a variety of different speeds and/or the engines exceed the
ability of reasonably sized mechanical transmissions. Diesel-Electric
is considerably more expensive than a mechanical transmission and is
not cost effective in boats with less than locomotive sized engines.

Ok - so if Navistar can make this work for utility lift trucks with
that kind of efficiency, would they work in boats?

I don't think so. Utlity lift trucks are constantly changing speeds,
most boats do not.