46 CFR §178.320

1. (a)As permitted by § 178.310(c) of this part, the following vessels may undergo the simplified stability proof test detailed in § 178.330 of this part, in the presence of a Coast Guard marine inspector, if they do not have tumblehome at the deck, measured amidships, that exceeds 2 percent of the beam:
   1. (1)Monohull vessels; and
   2. (2)Flush deck catamaran vessels which are not pontoon vessels and carry not more than 49 passengers.
2. (b)As permitted by § 178.310(c) of this part, a self-propelled pontoon vessel may undergo the pontoon simplified stability proof test detailed in § 178.340 of this part, in the presence of a Coast Guard marine inspector, if it satisfies all of the following requirements:
   1. (1)The vessel carries not more than 49 passengers and does not make international voyages;
   2. (2)The vessel operates on Protected Waters only;
   3. (3)The vessel is constructed with only one deck;
   4. (4)The buoyant hull volume consists of two symmetric, fully enclosed hulls;
   5. (5)The cross section of each hull is circular or of wall-sided construction without tumblehome, and constant for at least 90 percent of the length of the hull;
   6. (6)The hulls contain no machinery or tanks;
   7. (7)The portion of the deck accessible to passengers does not extend beyond—
      1. (i)The outboard edge of the hulls, and
      2. (ii)The forward or the aft end of the hulls;
   8. (8)There is no deck more than 0.15 meters (6 inches) above any point on any of the buoyant hulls;
   9. (9)The distance between the centerlines of the hulls is not less than 1.83 meters (6 feet); and
   10. (10)Each hull has a beam or diameter, as applicable, of not less than 0.61 meters (2 feet).
3. (c)For a vessel that carries not more than 49 passengers, carries no deck cargo, and is otherwise eligible to undergo the simplified stability proof test detailed in § 178.330 or § 178.340 of this part, the authority issuing the stability letter may—
   1. (1)Dispense with the requirements of the simplified stability proof test in § 178.330 or § 178.340 of this part when the vessel's stability can be adequately assessed by alternate means giving due consideration to each item that impacts a vessel's stability characteristics which include, but are not limited to, the form, arrangement, construction, number of decks, route, and operating restrictions of the vessel; or
   2. (2)Authorize a change in the requirements of the simplified stability proof test in either § 178.330 or § 178.340 of this part, when necessary to adequately assess the vessel's stability.