Ala. Code § 33-5-19: Certificates of Registration and Numbers Generally - Exemption from Numbering Provisions of Article.

A vessel shall not be required to be numbered under this article if it is:

(1) A vessel operating under valid temporary certificate or number;

(2) Already covered by a number in full force and effect which has been awarded to it pursuant to federal law or a federally approved numbering system of another state; provided, that such vessel shall not have been within this state for a period in excess of 90 consecutive days;

(3) A vessel under registry from a country other than the United States temporarily using the waters of this state;

(4) A vessel owned by the United States, or a state, county or municipality;

(5) A ship’s lifeboat; or

(6) A vessel not propelled by machinery, except sail boats and boats for hire.