Doesn't that implicitly depend on what you've fully laden?
Boats are usually weighed in a different manner than their
displacement is calculated. Don't even get started on "Thames measurement". You weigh a
boat in the slings, crudely (within 500 pounds, say). You calculate the displacement either by doing a back of the envelope calculation of the volume of the
hull form, or by putting a 12 x 6 x 40 foot
hull into a 15 x 10 x 45 foot box with enough
water to float it...and then seeing how far the
water goes up the wall. Taking a bath is you displacing water in a tub.
Guess what? The displacement is different in fresh and
salt water and warm and cold water. Look up "
Plimsoll line" for further partings of the curtain of mystery, although the short version is that is what all the numbered dashes on the bows of freighters mean: "load to here and no further in these conditions". Weight's not the issue. It's volume and the effects of the water on the buoyancy of the ship. You could tie a truck to the
deck of your
Morgan in the Dead Sea and creep quite cheerfully without decks awash. Try it in the
Great Lakes, and you're an amusing artificial reef.
Boats are often weighed at "empty", "light" and "laden" points. "Empty" is empty tankage and as close to no
gear as is possible. "Light" is, say, half
tanks and "normal"
safety gear, like an inshore or coastal cruiser would have, and "laden" would be "full
tanks, twenty cases of
beer, six month's of
food, all my dive gear, a
compressor, eight 4D
batteries, 500 pounds of chain and six anchors."
That's when you get to see if the waterline stripe has any bearing on reality.
Hope this has helped. Like "how long is a piece of rope", it's not a straightforward subject.