33 CFR §173.51

1. (a)This subpart applies to each vessel operated on waters subject to the jurisdiction of the United States and on the high seas beyond the territorial seas for vessels owned in the United States that:
   1. (1)Is operated by its operator for recreational purposes; or
   2. (2)Is required to be numbered under this part.
2. (b)This subpart does not apply to a vessel subject to inspection under Title 46 U.S.C. Chapter 33.