Section 178.320 - Intact stability requirements-non-sailing vessels(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) Monohull vessels; and(2) Flush deck catamaran vessels which are not pontoon vessels and carry not more than 49 passengers.(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) The vessel carries not more than 49 passengers and does not make international voyages;(2) The vessel operates on Protected Waters only;(3) The vessel is constructed with only one deck;(4) The buoyant hull volume consists of two symmetric, fully enclosed hulls;(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) The hulls contain no machinery or tanks;(7) The portion of the deck accessible to passengers does not extend beyond- (i) The outboard edge of the hulls, and(ii) The forward or the aft end of the hulls;(8) There is no deck more than 0.15 meters (6 inches) above any point on any of the buoyant hulls;(9) The distance between the centerlines of the hulls is not less than 1.83 meters (6 feet); and(10) Each hull has a beam or diameter, as applicable, of not less than 0.61 meters (2 feet).(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) 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) 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.USCG-2007-0030, 75 FR 78088, Dec. 14, 2010