Section 4B. Whoever removes, defaces, alters, changes, destroys, obliterates or mutilates, or causes to be removed or destroyed or in any way defaced, altered, changed, obliterated or mutilated, the identifying number or numbers of the manufacturer of a motorboat or the identification number of the manufacturer of a motor or engine designed for use in a boat with intent thereby to conceal the identity of such motorboat, motor or engine shall be punished by a fine of not more than five hundred dollars or by imprisonment for not more than one year, or both; and possession of any motorboat or any such motor or engine or of any part thereof, the identifying number or numbers of which have been so removed, defaced, altered, changed, destroyed, obliterated or mutilated shall be prima facie evidence of a violation of the foregoing provision. Whoever sells or otherwise disposes of or attempts to sell or otherwise dispose of such motorboat, motor or engine, knowing or having reason to believe that the identifying number or numbers of said motorboat, motor or engine have been so removed, defaced, altered, changed, destroyed, obliterated or mutilated, shall be punished by the same fine or imprisonment, or both.