What your discribing are two different types of numbers..

The builders number is the Hull Number and is like the VIN number on your
car and will be recorded in any state registation or if your going to
document the vessel.

The numbers and displacement info that is engraved into the beams is a
Documentation Number that is issued buy a Canadian Gov. agency for
Documented vessels. (in the US, that would be the US Coast Guard.)

The issued Documentation will remain the same even if the owner or buyer
fails to renew the documentation. The documentation my be retired but the
number remains assigned to that vessel and will be used if you reapply for
documentation status.

If you aren't going to reinstate the documentation then you will have to put
some type of recreational vessel registration numbers on the boat.. You can
use one or both of the numbers you have with your local agency.. They should
understand the difference between Builders Hull NO. and the Vessel Doc. NO.

Steve
s/v Good Intentions