Preamble
"(k) Every motor or steam vessel of more than fifteen gross tons but less than one hundred gross tons, operating for pleasure or any purpose other than the transportation of passengers or freight for hire or profit, shall be required to carry not less than one licensed navigator and one licensed engineer. Motor or steam vessels of fifteen gross tons or less shall be exempt from the provisions of this subsection subject to such conditions as the Insular Collector of Customs may require."