A PT boat was a motor torpedo boat used by the United States Navy in World War II. It was small, fast, and inexpensive to build, valued for its maneuverability and speed but hampered at the beginning of the war by ineffective torpedoes, limited armament, and comparatively fragile construction that limited some of the variants to coastal waters. In the US Navy they were organized in Motor Torpedo Boat Squadrons (MTBRONs).
PT-105, an 80' Elco boat, under way
PT-9 in June 1940
Second place PT-31 crossing the finish line during the "Plywood Derby".
Elco and Higgins PT boats, as published in a 1945 training manual
A motor torpedo boat is a fast torpedo boat, especially of the mid 20th century. The motor in the designation originally referred to their use of petrol engines, typically marinised aircraft engines or their derivatives, which distinguished them from other naval craft of the era, including other torpedo boats, that used steam turbines or reciprocating steam engines. Later, diesel-powered torpedo boats appeared, in turn or retroactively referred to as "motor torpedo boats" for their internal combustion engines, as distinct from steam powered reciprocating or turbine propulsion.
Israeli MTB formation, c. 1967
MTBs in the Mediterranean, February 1945
MTB-460 of the Royal Canadian Navy