Not quite all questions;
The Act for the Registration of British Vessels in 1845 and The Merchant Shipping Acts of 1854 :
that the property in a ship shall be divided into 64 shares;
that not more than 64 individuals shall be entitled to be registered at the same time as owners of any one ship;
that a person shall not be entitled to be registered as Owner of a fractional part of a share in a ship but any number of persons not exceeding five may be registered as joint owners of a ship or of any share or shares therein.
and previous to that;
A minute of the General Shipowners Society of December 11, 1823, records the Committee also conceive that the division of the property on ships, into sixty four assumed shares, upon the binary principle of halving the ship, and proportions under each, down to a sixty-fourth part, will be found in practice to be a more convenient system.
From http://www.lr.org/Images/25%2064%20Shares_tcm155-173538.pdf
I always thought Mike the Boilerman was a bit dodgy.
A corollary:
Does anyone know why this doesn't apply to canal boats;
"The British Registry Act of 1786, in the reign of George III, enlarged the scope of the boundary of registration and made it compulsory for every owner of a vessel of 15 tons or more to have the tonnage measurement ascertained and a certificate of registry to contain full particulars, dimensions etc."