Where is length measured for regulatory purposes?
Here is what David Pascoe has to say on the subject. Perhaps this will provide some help....
With the advent of integrally molded bow pulpits and built in swim platforms, there has been a lot of confusion over how a boat length should be properly represented. A few, though certainly a minority, of boat builders have included the bow pulpit in the length over all (LOA).
Most others use what is known as length on deck (LOD) that does not include the length of the pulpit....
There has long been much misunderstanding about the lengths and weights shown on Federally documented boats. How these numbers are derived goes back to the World War II days when many yachts were impressed into Coast Guarding services. At that time, the Coast Guard wanted to know the useable interior volume of the yachts. This was achieved through a procedure called admeasurement.
Therefore, the "Registered Length" shown on Federal documents represents an average of the length on deck and the length waterline. Basically, this number cuts the lengths of the overhangs at bow and stern in half. Thus, if you have a boat that is 50 feet on deck and 46 feet on waterline, the registered length will be 48 feet. The same holds true for the beam of the boat; it's an average between the widest point and the beam at water line.
-- Edited by Marin at 20:57, 2009-01-15