Where is length measured for regulatory purposes?

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Chris Foster

Senior Member
Oct 12, 2007
Vessel Name
Vessel Make
46 Grand Banks Classic
A buncha things change, regulation wise, at 12 meters boat length.

Any idea what measurement the CG uses to determine this?

Since it's 39'4", I'm over that from tip of the bow to back of the swim step.* The boat is called a 38, and that's pretty much stem-to-stern.* And the LWL is around 36.

Having a bell aboard has always seemed silly.* I don't have one, don't want to buy or install one.* But I'd also just as soon not get my pee-pee wacked if I'm inspected.
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....
...Registered Length

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
According to 33 CFR 183.3:

Length means the straight line horizontal measurement of the overall length from the foremost part of the boat to the aftermost part of the boat, measured from end to end over the deck excluding sheer, and measured parallel to the centerline. Bow sprits, bumpkins, rudders, outboard motor brackets, handles, and other similar fittings, attachments, and extensions are not included in the measurement.

The code is here: http://www.uscgboating.org/regulations/fedreg.htm

The part above is from the definitions page here: http://edocket.access.gpo.gov/cfr_2004/julqtr/pdf/33cfr183.3.pdf

-- Edited by gns at 22:25, 2009-01-15
Been a while but I thought the bell requirement was canceled for most smaller boats.

Check the Hooligaan Navy web site , not a brochure written years ago.

When I was boarded by the CG for a "safety inspection" I refused to allow them to leave until they inspected my bell. I paid alot*for that thing.

Chris Foster wrote:

*But I'd also just as soon not get my pee-pee wacked if I'm inspected.
Do I hear some Cheech and Chung there?

You might also ask... "Where is length measured for slip and mooring rentals".* Up here in New England where overnight*transient*rates are ridiculous, slips go for $3.50 - $8.50 (Newport) per foot.* Transient moorings used to go for fixed rates of $20 - $30 per night, but recently, many marinas are moving to per foot rates of around*$1 - $1.50 per foot), except for Nantucket, charging $60 - $100 per night + tax, based on length.*

As such, we have to play a little game with the marinas.* With intergrally molded swim platforms, all Nordic Tug model lengths are understated.* With a LOA of 33' 10", not including the one foot anchor roller overhang,*and a LWL of 32' 8", my NT 32 averages 33'.* While most marinas will accept the "Nordic Tug 32" graphics on my hull, some marinas have actually measured the length and charged me for 34 feet.

John Baczek
Puffin, NT32-266
Watch Hill, RI
Inland and International Navigation rules:

Rule 33

(a) A vessel of 12 meters or more in length shall be provided with a whistle and a bell [INLD], a vessel of 20 meters or more in length shall be provided with a bell in addition to a whistle [Intl], and a vessel of 100 meters or more in length shall, in addition be provided with a gong, the tone and sound of which cannot be confused with that of the bell. The whistle, bell and gong shall comply with the specifications in Annex III to these Regulations. The bell or gong or both may be replaced by other equipment having the same respective sound characteristics, provided that manual sounding of the prescribed signals shall always be possible.

(b) A vessel of less than 12 meters in length shall not be obliged to carry the sound signaling appliances prescribed in paragraph (a) of this Rule but if she does not, she shall be provided with some other means of making an efficient signal.

Annex III

Subpart B - Bell or gong

§ 86.21 Intensity of signal
A bell or gong, or other device having similar sound characteristics shall produce a sound pressure level of not less than 110 dB at 1 meter.

§ 86.23 Construction
Bells and gongs shall be made of corrosion-resistant material and designed to give a clear tone. The diameter of the mouth of the bell shall be not less than 300 mm for vessels of more than 20 meters in length, and shall be not less than 200 mm for vessels of 12 to 20 meters in length. The mass of the striker shall be not less than 3 percent of the mass of the bell. The striker shall be capable of manual operation.

NOTE: When practicable, a power-driven bell striker is recommended to ensure constant force.


wingspar wrote:

When I was boarded by the CG for a "safety inspection" I refused to allow them to leave until they inspected my bell. I paid alot*for that thing.

Ditto!* Although it took me a while to dig it out of the locker under the pilothouse!

We were at Port Aransas Muni Marina and their rates were based on "under 30 feet" and "over 30 feet". Well I had a Prairie 29. The P29 is a HUGE 29ft boat(in actuality it is 29ft7in LOD). It looks big. The harbormaster came out and was writing me up and asked how big the boat was. When I said 29ft, he almost lost it. He would not hear any of it and charged me the 30+ rate. It was not very expensive so I didn't fight him but i was kinda funny.
ON the right coast ICW , many marinas are simply 1/4 mile or more of dock , along the river.

No sense in B-S , they ALL tape measure how much room you take , bowsprit to dink on davits.

Seems fair to pay for what you get.

Thanks for the replies.* I was pretty certain that I was indeed under 12 meters (or metres for our friends in the Great White North)... but wasn't certain exactly what the definition would be.

The Anacortes marinas are real strict about the tip-to-tail measurement - not just for the income, but because the fairways are pretty bloody narrow, too.* My former marina neighbor's boat was being chartered last summer.* As they were departing, they tried to pass beam-to-beam with another boat in the fairway and discovered that*a molded-in bowsprit sticking into the fairway (against marina rules) could do plenty of damage.*
How the Coast Guard measures a boat for regulatory purposes and how a marina measures a boat for moorage purposes have nothing to do with each other. But it is fun to read about different experiences. I, too, have had my boat measured using different criteria at different marinas. When in doubt they usually go high.
You would be amazed at the number of sports that used to come to our dock and report the LWL!!

Now we flat rate , no more liars. EZ

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