Re: how do manufacturers determine hp for their boats?
Code of Federal Regulations<br /><br />Title 33: Navigation and Navigable Waters<br />PART 183BOATS AND ASSOCIATED EQUIPMENT <br />Subpart DSafe Powering <br /><br /><br />§ 183.53 Horsepower capacity.<br />The maximum horsepower capacity marked on a boat must not exceed the horsepower capacity determined by the computation method discussed in paragraph (a) of this section, or for certain qualifying boats, the performance test method discussed in paragraph (b) of this section.<br /><br />(a) The maximum horsepower capacity must be computed as follows:<br /><br />(1) Compute a factor by multiplying the boat length in feet by the maximum transom width in feet excluding handles and other similar fittings, attachments, and extensions. If the boat does not have a full transom, the transom width is the broadest beam in the aftermost quarter length of the boat.<br /><br />(2) Locate horsepower capacity corresponding to the factor in Table 183.53.<br /><br />(3) For a boat with a factor over 52.5, if the horsepower capacity calculated in Table 183.53 is not an exact multiple of 5, it may be raised to the next exact multiple of 5.<br /><br />(4) For flat bottom hard chine boats with a factor of 52 or less, the horsepower capacity must be reduced by one horsepower capacity increment in Table 183.53.<br /> <br /><br /> Table 183.53_Outboard Boat Horsepower Capacity<br /> [Compute: Factor=Boat LengthxTransom Width]<br /> <br /> <br /> <br />If factor (nearest integer) is...................... 0-35 36-39 40-42 43-45 46-52<br />----------------------------------------------------------------------------------------------------------------<br />Horsepower Capacity is.............................. 3 5 7.5 10 15<br />----------------------------------------------------------------------------------------------------------------<br /> <br />[Note: For flat bottom hard chine boats, with factor of 52 or less, reduce one capacity limit (e.g. 5 to 3)]<br /><br /><br /> <br /><br /> <br />----------------------------------------------------------------------------------------------------------------<br /> No remote steering, or less than 20[sec] transom<br /> Remote steering and at height<br /> If factor is over 52.5 and the boat least 20[sec] transom -------------------------------------------------<br /> has height For flat bottom hard<br /> chine boats For other boats<br />----------------------------------------------------------------------------------------------------------------<br />Horsepower capacity is (raise to (2xFactor) -90......... (0.5xFactor)-15........ (0.8xFactor)-25<br /> nearest multiple of 5).<br />----------------------------------------------------------------------------------------------------------------<br /><br /><br />(b) For boats qualifying under this paragraph, the performance test method described in this paragraph may be used to determine the horsepower capacity.<br /><br />(1) Qualifying criteria. (i) Thirteen feet or less in length;<br /><br />(ii) Remote wheel steering;<br /><br />(iii) Transom height<br /><br />(A) Minimum 19 inch transom height; or, <br /><br />(B) For boats with at least a 19 inch motorwell height, a minimum 15 inch transom height;<br /><br />(iv) Maximum persons capacity not over two persons;<br /><br />(2) Boat preparation. (i) The boat must be rigged with equipment recommended or provided by the boat and motor manufacturer and tested with the highest horsepower production powerplant for which the boat is to be rated, not to exceed 40 horsepower.<br /><br />(ii) Standard equipment must be installed in accordance with manufacturers' instructions.<br /><br />(iii) The lowest ratio (quickest) steering system offered on the boat model being tested must be installed.<br /><br />(iv) The outboard motor must be fitted with the manufacturer's recommended propeller providing maximum speed.<br /><br />(v) Standard permanently installed fuel tanks must be no more than one-half full. Boats without permanent tanks must be tested with one full portable tank.<br /><br />(vi) Portable tanks must be in their designated location or placed as far aft as possible.<br /><br />(vii) The outboard motor must be placed in the lowest vertical position on the transom or, if mounting instructions are provided with the boat, at the height recommended.<br /><br />(viii) Boat bottom, motor and propeller must be in new or almost new condition.
