With the benefit of experience gained from the first-generation PT boats and a deadline looming to select designs for mass production, in July and August 1941 the USN invited all firms involved in PT boat design to take part in a series of endurance tests in Long Island Sound. Each design had to complete a 190NM high-speed endurance test. The boats were being evaluated not only for speed, but for durability and maneuverability. Contenders included prototypes from Elco, Higgins, the Huckins Yacht Corporation of Jacksonville, Florida, and PT-8 from the Philadelphia Navy Yard. The event was given the unofficial nickname “The Plywood Derbys.”

The winner of the trials was PT-20, the first of the Elco 77ft PT boats. Higgins’s 78ft PT-70 was also impressive. PT-69, the Huckins 72ft PT boat, showed enough promise to generate a contract for 18 boats to be used for training and coastal patrol duties. Overall, the most promising boats emerging from the contest were the Elco design and the Higgins 78ft design. In particular, the Higgins boat was praised for its smooth handling. After some final tweaks prompted by the USN’s requirement for a larger PT boat to carry more ordnance, both firms were given contracts for mass production. Elco was awarded a contract to build 36 of its slightly enlarged 80ft design in Bayonne, while Higgins began production of 24 of their 78ft design in New Orleans.

This view shows the engine room of Higgins 78ft PT boat PT-625, later transferred to the Soviet Union under Lend Lease. Almost all USN PT boats were powered by the same type of engine. Designed especially for PT boats,
the Packard 4M-2500 marine engine ran on 100-octane aviation gasoline and developed up to 1,500hp. Three engines powered each boat with each engine driving its own propeller shaft. To be successful, a PT boat had to be fast; when the engines were performing up to specifications and the hull was clean, speeds in excess of 40kn could be easily achieved. (NHHC NH 71679)

THE ELCO 77FT PT BOAT

The standard displacement of these boats was 33 tons. Construction was almost entirely wood with aluminum only used on the bridge structure. No armor protection was fitted as designed, but later boats received armor around the bridge. For a boat this size, it was packed with weapons. Most importantly, each boat could mount four 21in torpedo tubes, each with a torpedo that fired forward only. If only two torpedoes were embarked, space and weight became available for up to eight depth charges. Originally, each boat carried two twin .50-caliber mounts abaft the bridge in hydraulically powered aircraft-type turrets for antiaircraft protection. Two single mounts for .30-caliber Lewis machine guns were fitted forward of the bridge.

THE ELCO 80FT PT BOAT

Elco modified its 77ft PT boat design throughout the war. An 80ft version was introduced beginning with PT-103. A total of 358 of these boats were delivered from the company’s Bayonne yard, making it the most produced PT boat variant. Though only 3ft longer than the previous version, they looked much larger because of their higher freeboard. They were also more rugged than the shorter boats. For armament, the 80ft version mounted the standard four 21in torpedo tubes and two .50-caliber machine-gun turrets. Added to this weapons suite was a single mount 20mm Oerlikon cannon aft. Based on local requirements and the availability of weapons, other weapons augmented the gun battery. Several combinations were used, including a second 20mm mount, a 37mm gun, or a 40mm Bofors mount.

Higgins 78ft PT boats were built on an assembly line at Higgins Industries’ City Park Plant, New Orleans, Louisiana, as shown here. The company produced a
total of 146 of these boats for the USN, making it the second most numerous PT boat in service. Another 46 were delivered to the Soviet Union and seven to the Royal Navy. (NHHC NH 44482)

THE HIGGINS 78FT PT BOAT

The first Higgins 78ft PT boats were delivered in July 1942. In total, the New Orleans facility produced 221 of these boats of which PT-71 through PT-94 were 78ft, PT-265 through PT-313 and PT-450 through PT-485 were 78ft 6in, and the last batch, PT-791 through PT-802, were 78ft 8in. They were all armed as per the Elco PT boats.

PT BOAT WEAPONS

The sole reason the PT boat existed was to launch torpedoes against the enemy. For the first two years of the war, USN PT boats were crippled in this regard because they carried unreliable and often defective torpedoes. Beginning in mid-1943, the 22.5in Mk XIII torpedo was introduced on PT boats. Originally an aircraft torpedo with a top speed of 33.5kn and a range of 5,500yd, it possessed a warhead consisting of 600lb of Torpex. At the start of the war, the Mk XIII also had reliability issues, but these were addressed by mid-1943. Because it was much smaller and lighter than the Mk VIII, it did not require a torpedo tube to facilitate its launch (it could simply be rolled into the water from a side rack), which meant there was an appreciable weight saving due to the Mk XIII’s smaller size and lighter weight and the absence of torpedo tubes.

For their weight, the PT boats were heavily armed craft. In addition to the four torpedoes, a number of guns and cannons were embarked. The first boats carried only two pairs of .50-caliber machine guns mounted in two turrets. These were intended to provide some measure of antiaircraft protection but could also be used to engage surface targets. Augmenting the machine guns early in the war was one or two 20mm cannons, usually fitted on the aft portion of the boat and also capable of engaging both air and surface targets.

When the PT boats turned their attention to Japanese barges, often armored and provided with guns larger than 20mm, it became apparent that the boats required larger-caliber weapons. In early 1943, a 37mm antitank gun was fitted on the bow to gain the upper hand against barges. Later that year, a 37mm automatic cannon from the USAAF became available. Beginning in August 1943, 40mm single Bofors mounts were experimented with. This proved to be an ideal anti-barge weapon with a high rate of fire, adequate range, and the capability to defeat any armor protection fitted on a barge.

Extract from USN PT Boat vs IJN Destroyer: Tokyo Express 1942–43 by Mark Stille.