Haw. Rev. Stat. § 200-30: Reciprocal agreements and courtesy.

The department may enter into, amend, revise, suspend, or revoke reciprocal agreements or arrangements with appropriate and duly authorized agencies of other jurisdictions whereby vessels properly numbered and equipped under the laws and regulations of this State are granted the same or substantially similar privileges, exemptions, and benefits enjoyed by vessels properly registered and equipped in such other jurisdictions in exchange for substantially similar privileges, exemptions, and benefits granted to properly registered and equipped vessels from other jurisdictions by the State. The department by appropriate rules may define the extent and nature of privileges, exemptions, and benefits which may be extended, as a matter of courtesy, to vessels properly numbered and equipped in other jurisdictions not covered by reciprocal agreements or arrangements.

Notwithstanding the preceding language of this section, the department shall recognize the validity of a number awarded to any vessel by:

(1) Another state under a numbering system approved by the Coast Guard under appropriate federal laws and requirements; or

(2) By the Coast Guard, for a period of at least sixty days.