The Safety Convention and the requirements therein, unless it is otherwise provided by regulations made under this Act, shall not apply to—
(a) ships of war and troop ships;
(b) cargo ships of less than 500 gross tons with respect to Safety Convention requirements other than those for radio;
(c) cargo ships of less than 300 gross tons with respect to Safety Convention requirements for radio;
(d) ships not propelled by mechanical means;
(e) wooden ships of primitive build;
(f) pleasure yachts not engaged in trade;
(g) fishing vessels.