Cal. Veh. Code § 9854

The owner of any vessel already covered by a number in full force and effect that has been issued to it pursuant to then operative federal law or a federally approved numbering system of another state shall make application within 30 days after the 60-day reciprocity period provided for in Section 9873. Such application shall be in a manner and pursuant to the procedure required for the issuance of a number under Section 9853.