Next time someone asks you how long your boat is, you'd better get out your tape-measure to be sure. The figure that the manufacturer uses for identifying the vessel – as in a Mainship 45 or a Grand Banks 47 – may not reflect the actual length.
MAINSHIPMainship's 45 trawler was once sold as a 43.Boat-builders aren't necessarily trying to deceive you. The small-print specifications contained in advertising brochures and broker listings generally provide accurate numbers. But the moniker given the boat for marketing purposes – well, all we can say is, don't believe everything you read.
Examples abound. The Grand Banks 44, for example, became the Grand Banks 47 in later models without any change in the actual distance between bow and stern. The Mainship 43 became the Mainship 45. At Nordic Tugs, the company's 47 became a 49 and its 52 became a 54. In fact, this year's Nordic Tug 32 is actually almost three feet longer than the name might imply.
"We call her a 32, but she's really 34 feet 7 inches of comfort and convenience!" the Nordic Tug website boasts, making a virtue out of what some might consider a disparity.
UNDERSTANDING STANDARDS
Admittedly, none of these practices is new. Boat manufacturers have been taking liberties with length figures for at least several decades now, says Dave Gerr, director of the Westlawn Institute of Marine Technology, a school for yacht designers headquartered in Mystic, Connecticut. 
The practice began with sailboats, where manufacturers had to meet limitations set down by various racing organizations. If a boat was 29 feet 11 inches long and had to be smaller to qualify for entry into a race, they called it a 29-foot boat. Soon the system spread to powerboat makers as well, and now it is standard everywhere, Kerr says.
Of course, there are some standards for measuring boat length. Coast Guard regulations define boat length – known in the U.S. as length overall, or LOA – as "the horizontal distance between bow and stern, excluding fittings and attachments" that aren't actually a part of the hull.
That means you can't officially include such protuberances as bowsprits, rudders, outboard motors or swim platforms in describing the vessel's length, according to the Code of Federal Regulations 46, part 69, subpart E (Measurements of Vessels).
The American Boat and Yacht Council, which sets voluntary technical practices and engineering standards for the recreational boating industry nationwide, offers a similar definition. ABYC standard S-8 defines length overall as "the straight line measurement from the foremost part of the boat to the aftermost part of the boat, measured parallel to the centerline and to the design waterline."
It adds that while "integrally formed, molded or welded components and appendages" such as bow pulpits, swim platforms and attachment structures for the propulsion systems should be included in the LOA measure, "attached bowsprits, pulpits, boomkins, rudders, sails, outboard brackets, handles, railings, and other similar attached extensions are not."
"Specifications and advertising for recreational boats shall clearly indicate the particular parameter being specified (e.g., length overall or length waterline)," the S-8 language prescribes.
