Jay Honeck wrote:

A boat -- especially an ocean-going yacht -- almost never leaves dock. But
when it does, you go very slowly, usually in seas that make our "turbulence"
seem pretty tame, don't get very far, and you had better have a high credit
limit on your Visa card, cuz re-filling those tanks ain't pretty.


You know an awful lot about boats for a guy who lives in a place where
the biggest body of water most people ever see has a four legs and a
drain at the bottom

What you're referring to is a motor yacht designed for bombing around
near coastal waters. Aside from the sportfishers that may go offshore,
these boats stay within sight of shore and have their range severely
limited by fuel needs. "Turbulence" out there is no worse than we get
in the air and often less, especially in the summer. Most of these
boats have no business in serious weather.

If you want to see a true oceangoing yacht, look at something like the
Nordhavn 62'. These "expedition yachts" are becoming much more popular
and look more like commercial ships than speedboats. The N62 is
designed to run at 9 knots on a single 225HP diesel engine turning a
40" propeller at very low RPM. A typical 40' coastal stinkpotter will
run 2x450hp engines turning surface-penetrating props that look like
they came out of a blender. The Nordhavn doesn't go fast but with 2500
gallon tanks it can cross an ocean without stopping, and those big slow
diesels are built to run for weeks on end. 2MPG may sound awful but
keep in mind the boat weighs 80 tons (!). And it's bigger inside than
most condos:

http://www.nordhavn.com/62/interiorThumbs.php4

The key is speed. A boat runs most efficiently at "hull speed" which is
a function of length. If you want to push the hull faster than that,
fuel consumption goes up ridiculously, even worse than with airplanes.

-cwk.