PT boat


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 USN they were organized in Motor Torpedo Boat Squadrons.
The PT boat was very different from the first generation of torpedo boat, which had been developed at the end of the 19th century and featured a displacement hull form. These first generation torpedo boats rode low in the water, displaced up to 300 tons, and had a top speed of. During World War I Italy, the US and UK developed the first high-performance petrol-powered motor torpedo boats and corresponding torpedo tactics, but these projects were all quickly disbanded after the Armistice. World War II PT boats continued to exploit some of the advances in planing hull design borrowed from offshore powerboat racing and by using multiple lightweight but more powerful marinized aircraft-derived V-12 engines were able to grow in both size and speed.
During World War II, PT boats engaged enemy warships, transports, tankers, barges, and sampans. As gunboats they could be effective against enemy small craft, especially armored barges used by the Japanese for inter-island transport. Several saw service with the Philippine Navy, where they were named "Q-boats".
Primary anti-ship armament was four 21-inch Mark 8 torpedoes, each had a TNT warhead and had a range of at. Two twin.50-inch M2 Browning heavy machine guns were mounted for anti-aircraft defense and general fire support. Some boats carried a Oerlikon cannon.
Propulsion was via a trio of Packard 4M-2500 and later 5M-2500 supercharged gasoline-fueled, liquid-cooled V-12 marine engines.
Nicknamed "the mosquito fleet" and "devil boats" by the Japanese, the PT boat squadrons were hailed for their daring and earned a durable place in the public imagination that remains strong into the 21st century. Their role was replaced in the U.S. Navy by fast attack craft.

Development

At the outbreak of war in August 1914, W. Albert Hickman devised the first procedures and tactics for employing fast maneuverable seaworthy torpedo motorboats against capital ships, and presented his proposal to Rear Admiral David W. Taylor, the Chief of the US Navy's Bureau of Construction and Repair. In September 1914, Hickman completed plans for a "Sea Sled" torpedo boat and submitted these to the Navy in hopes of obtaining a contract. While favorably received, Secretary of the Navy Josephus Daniels rejected the proposal since the US was not at war, but Hickman was advised to submit his plans and proposal to the British Admiralty, which was done the following month. The Admiralty found it interesting but thought that "no fast boat of 50' to 60'
length would be sufficiently seaworthy", so Hickman built and launched his own privately financed Sea Sled capable of carrying a single 18-inch Whitehead Mark 5 torpedo. In February 1915, this Hickman sea sled demonstrated speeds in rough winter seas off Boston to both US and foreign representatives but again, he received no contracts. The Admiralty representative for this sea sled demonstration was Lieutenant G.C.E. Hampden. In the summer of 1915, Lieutenants Hampden, Bremner, and Anson approached John I. Thornycroft & Company about developing a small high speed torpedo boat, and this effort eventually led to the Coastal Motor Boat which first went into service in April 1916.
Meanwhile, in August 1915, the General Board of the United States Navy approved the purchase of a single experimental small torpedo boat that could be transportable. This contract for C-250 ended up going to Greenport Basin and Construction Company, of Greenport, NY. When it eventually was delivered and tested in the summer of 1917, it was not deemed a success, so a second boat of the sea sled design was ordered from Hickman in either late 1917 or early 1918. Using his previous design from September 1914 and the previous unsuccessful bid for C-250, the new boat C-378 was completed and fully tested just in time to be cancelled by the Armistice. With a full loaded weight of 56,000 pounds, C-378 made a top speed of with, and maintained an average speed of in a winter northeaster storm with seas, which would still be considered exceptional even 100 years later. The Sea Sled would not surface again as a torpedo boat topic until 1939, but would continue to be used by both the Army and Navy as rescue boats and seaplane tenders during the 20s and 30s. In 1922, the US Navy reconsidered using small internal combustion engine powered torpedo boats. As a result, two types and of British Royal Navy Coastal Motor Boats were obtained for testing. The larger boat was used for experiments until 1930. In 1938, the U.S. Navy renewed their investigation into the concept by requesting competitive bids for several different types of motor torpedo boats, but excluded Hickman's Sea Sled. This competition led to eight prototype boats built to compete in two different classes. The first class was for boats, and the second class was for boats. The resulting PT boat designs were the product of a small cadre of respected naval architects and the Navy.
On 11 July 1938, invitations to builders and designers were issued with prizes awarded for the winning PT boat designs given out on 30 March 1939. In an important note after winning the design competition for the smaller PT boat, George Crouch wrote that Hickman's Sea Sled design would be far superior "in either rough or smooth water to that of the best possible V-bottom or hard chine design". Earlier when Sea Sleds were specifically excluded, Crouch had informed the Bureau of Ships that the Sea Sled was the best type of vessel for the job. On 8 June 1939, contracts were let to the Fogal Boat Yard, Inc., later known as the Miami Shipbuilding Co., of Miami, Florida, for PT-1 and -2 "Crash Boats", and to the Fisher Boat Works, Detroit, Michigan, for PT-3 and -4. These four boats were designed by George Crouch, and modified in some details by the Bureau of Ships.
Then, three additional boats were built by Andrew Higgins of Higgins Industries in New Orleans. These boats were PT-5 and PT-6 and then PT-6 "Prime" which was redesigned by Andrew Higgins personally using his own methods. Later that same year, Higgins was to build PT-70 that incorporated slight improvements over PT-6 Prime.
The Philadelphia Navy Yard simultaneously began construction of two other boats, created by designers at the Navy Yard and the Navy Bureau of Ships. These boats were constructed mainly out of aluminum and had 4 engines.
Later, rigorous testing performed on each design as well as changes in armament revealed limitations or problems that had to be fixed before they could meet required performance specifications. As a result, the Navy ordered further investigation and refinement of the existing designs until a satisfactory working design could be obtained.
At the same time, Henry R. Sutphen of Electric Launch Company and his designers visited the United Kingdom in February 1939 at the Navy's request to see British motor torpedo boat designs with a view to obtaining one that could be used as a check on the Navy's efforts. While visiting the British Power Boat Company, they purchased a private venture motor torpedo boat design - PV70 -, designed by the power boat racer Hubert Scott-Paine. PT-9 was to serve as the prototype for all the early Elco PT boats. After the initial competition, in late 1939, the Navy contracted Elco to build 11 copies of PT-9.
The final PT boat design competitor was Huckins Yacht Corporation of Jacksonville, Florida. On 11 October 1940, an agreement between the Navy and Huckins was finalized. The Navy would provide engines, and Huckins would build a PT boat at their own expense, with the caveat that the boat would be offered to the Navy for a later sum. This boat was a boat that became PT-69. Huckins reported a profit of $28.60 on this transaction.

Plywood Derby

Background

In March 1941, during a heavy weather run from Key West to New York by Motor Torpedo Boat Squadron 2, Elco 70-footers pounded heavily in waves even at moderate speeds, and seas continuously broke high over the bows. Operating personnel reported extreme discomfort and fatigue. All boats suffered from some sort of structural failure: forward chine guards ripped away, bottom framing under bows broken, side planking cracked , and other weaknesses. In April 1941, MTBRON 1 reported enthusiasm over the 81-foot Higgins, and with the Higgins showing such good seakeeping further purchase of Scott-Paine boats was unnecessary. And, in early 1941, the U.S. Navy Bureau of Ships lent Packard engines to both Huckins and Higgins, which wanted to build competitive boats at their own expense.
A Chief of Naval Operations PT Boat Conference convened in May 1941 to discuss future PT characteristics. All PTs prior to the Elcos had been found defective, and it was probable the extended Elco would not be an improvement. This conference, including representatives from BuShips, BuOrd, MTBRONs, Interior Control Board, and CNO, recommended a series of comparative tests to evaluate what turned out to be five new designs of motor torpedo boats. The conference strongly recommended that no more Elco 77-footers be ordered until the tests had shown that they were indeed satisfactory.

The Board of Inspection and Survey

The Board of Inspection and Survey, headed by Rear Admiral John W. Wilcox, Jr., conducted comparative service tests off New London, 21 to 24 July 1941, using the following boats:
Each member of the Board conducted an independent inspection of every boat class, evaluating them for structural sufficiency, habitability, access, arrangement for attack control, and communication facilities.
Boats were also evaluated under two conditions of armament loading: loaded and fully equipped with four torpedoes and sufficient fuel to operate 500 NM at 20 knots; and fully loaded with two torpedoes and ten depth charges with sufficient fuel to operate at.
Boats would have their tactical parameters of each design determined by photographs from an airship.
First open-ocean trial
Lastly, there was a demonstration of seakeeping qualities and hull strength by making a run at maximum sustained speed in the open ocean. Accelerometers were installed in the pilot house of each design to record "pounding". Conducted 24 July 1941, this open-water trial, at full throttle, would forever after be referred to by PT personnel as the "Plywood Derby." The course started from the mouth of New London Harbor, to Sarah Ledge, then led around the eastern end of Block Island, then around Fire Island Lightship, finishing at Montauk Point Whistling Buoy.
At the time, only the Elco 77-footers was loaded with armament. The other competitors had copper ingots added topside to make up the difference. This resulted in severe conditions for several of the boats during the trial and accounted for the transverse failure in PT-70s deck and subsequent hull failure as the copper fell into the hull.
Nine boats participated in the trial, and six boats completed the trial; PT-33 suffered structural damage off Block Island and withdrew, PT-70 withdrew after damaged by the ingots, and MRB developed engine trouble at the start of the run and withdrew.
By class, PT-20, the Elco 77-footer, came in first with an average speed of ; followed by PT-31, with an average speed of ; PT-69, the Huckins boat, with an average speed of ; PT-6, the Higgins 81-footer, with an average speed of ; and PT-8, the Philadelphia Navy Yard boat last, at. The other two Elco boats, PT-30 and PT 23, followed PT-31, placing before PT-69.
The accelerometers ranked the boats as follows: first was the Philadelphia Navy Yard PT-8 with the least pounding, second was the Huckins PT-69, third was the Higgins PT-6, and last were the Elco 77-footers.
Second open-ocean trial
Due to the problem with ingot loading, a trial with the PTs fully fitted out was conducted on August 12, 1941. Four boats - PT-8, PT-69, PT-70, and MRB - returned and Elco sent two new boats, PT-21 and PT-29. During this trial, boats faced heavier seas, as high as. All except the Huckins completed the run. The Huckins withdrew due to bilge stringer failure. The Higgins 76-footer completed the entire run but also suffered structural failures, attachments between planking and web frames pulling loose, and deck fastenings in the neighborhood of engine hatches showing extensive failures. PT-21 suffered minor cracks in the deck in the same location, but not to the same extent, as previously observed in PT-26, PT-30, and PT-33. PT-29 was assigned as a pace boat with PT-8 in order to generate a pounding comparison.
The average speed results from the course were: Elco 77-footer, ; Higgins 76-footer, ; Higgins MRB and Philadelphia Navy Yard boat,. Accelerometers were again installed in the pilot house of each boat, but the readings were incomplete because the violent motion of the boats made observations extremely difficult and in some cases necessitated abandonment of the observing stations. Further, many of those taken were beyond the normal range of the instruments and were considered inaccurate. Elco boats were found to pound heavily and confirmed previous reports of their discomfort.

Board of Inspection and Survey's findings

The Elco 77-Footer Design Demonstrates:
  1. Ability to make a maximum sustained speed of 39.7 knots; maximum speed 44.1 knots with heavy ordnance load.
  2. Maneuverability satisfactory except for a large turning circle of.
  3. Space available for four 21" torpedo tubes.
  4. Structural weaknesses resulting in transverse fractures of deck planking.
  5. Tendency to pound heavily in a seaway.
  6. Fittings and finish unnecessarily refined.
  7. Cost to the Government fully equipped $302,100.
The Huckins 72-Foot Design Demonstrates:
  1. Ability to make a maximum sustained speed of 33.8 knots; maximum speed 43.8 knots with light ordnance load.
  2. Maneuverability satisfactory with a turning circle of.
  3. Space available for two 21" torpedo tubes and ten depth charges.
  4. Structural weaknesses resulting in fracture of bilge stringers.
  5. Very little tendency to pound in a seaway.
  6. Fittings and finish appropriate for a motor torpedo boat.
  7. Cost to the Government fully equipped $263,500.
The Navy Yard Philadelphia 81-Foot Design Demonstrates:
  1. Ability to make a maximum sustained speed of 30.7 knots; maximum speed 33.9 knots with light ordnance load.
  2. Maneuverability unsatisfactory due to inability to reverse outboard engines with a large turning circle of
  3. Space available for two 21" torpedo tubes and ten depth charges.
  4. Structural strength is adequate.
  5. Tendency to pound severely in a seaway.
  6. Fittings entirely too heavy and cumbersome for this type of craft. Finish adequate.
  7. Cost to the Government fully equipped $756,400.
The Higgins 81-Foot Design Demonstrates:
  1. Ability to make a maximum sustained speed of 31.4 knots; maximum speed 34.3 knots with heavy ordnance load.
  2. Maneuverability satisfactory with a turning circle of 368 yards.
  3. Space available for four 21" torpedo tubes.
  4. Structural strength adequate.
  5. Moderate tendency to pound in a seaway.
  6. Fittings and finish satisfactory.
  7. Cost to the Government fully equipped $206,600.
The Higgins 76-Foot Design Demonstrates:
  1. Maximum sustained speed of 27.2 knots in rough seas; maximum speed 40.9 knots.
  2. Maneuverability satisfactory, turning circle not determined photographically, estimated 300 yards.
  3. Space available for four 21" torpedo tubes.
  4. Structural weaknesses caused failures in transverse bottom framing, separation of side planking from framing and extensive failures of deck fastenings.
  5. Moderate tendency to pound in a seaway.
  6. Fittings and finish satisfactory.
  7. Cost to the Government fully equipped $265,500.
The Board arrived at the following recommendations:
  1. That the Packard power plant having been found highly satisfactory be adopted as standard for future construction.
  2. That the ordnance installation of future motor torpedo boats consist of two torpedo tubes, machine guns and depth charges.
  3. That the Huckins 78-foot design be considered acceptable for immediate construction.
  4. That the Higgins 80-foot design suitably reduced in size to carry such ordnance loads as are required by our Navy be considered acceptable for immediate construction.
  5. That the Elco 77-foot design be considered acceptable for future construction provided changes in the lines are made to reduce the tendency to pound in a seaway, and the structure be strengthened in a manner acceptable to the Bureau of Ships.
  6. That the Philadelphia 81-foot boat be stripped of excess weight and be re-engined with three Packard engines.
The Board also had the following opinion on structural sufficiency: "During the first series of tests the Huckins design, the Philadelphia design and the Higgins design completed the open sea endurance run without structural damage. The Higgins 70' boat did not complete this run because of engine trouble. The Higgins 76' and boats of the Elco 77' developed structural failures even under moderate weather conditions prevailing. In the interval between the first and second test periods the PT-70 was repaired and an effort made to eliminate the causes of the structural failures. However, during the second endurance run, which was made in a very rough sea for this size boat, structural failures again occurred in PT-70. PT-69 and PT-21 experienced structural failures during the second run though these were much localized as compared with those found on PT70. The Board is of the opinion that certain changes in design are required to enable PT-69 and boats of the PT-20 Class to carry safely their military loads in rough weather."

Analysis of the "Plywood Derby" findings

The Board results provided very important benchmarks in the infancy of PT boat development. This type of craft presented design challenges that were still issues decades after, but there are some significant conclusions from the above recommendations and their order of merit. Those are:
  1. The Packard were the engines of choice.
  2. The Huckins 72-foot and a reduced Higgins 81-foot design were to be placed into production. Following an October 1941 BuShips conference and its new set of navy design requirements which included room to support four torpedoes and an upper length restriction of 82', the next two orders for pre-war PT boats were awarded to Higgins and Huckins.
  3. Even though the Elco 77-footers posted the fastest speeds, all seven Elcos suffered from structural damage and severe pounding causing the Board to recommend a redesign to correct these deficiencies. Elco competed for the PT-71 to PT-102 contract but did not win due to their higher unit price. After the start of the war and significantly revising their unit cost, Elco received the next PT boat order after Higgins and Huckins. This was to be their new Elco 80-foot design.

Elco

The Elco Naval Division boats were the longest of the three types of PT boats built for the Navy used during World War II. By war's end, more of the Elco boats were built than any other type of motor torpedo boat. The wooden-hulled craft were classified as boats in comparison with much larger steel-hulled destroyers, but were comparable in size to many wooden sailing ships in history. They had a beam. Though often said to be made of plywood, they were actually made of two diagonal layered thick mahogany planks, with a glue-impregnated layer of canvas in between. Holding all this together were thousands of bronze screws and copper rivets. This type of construction made it possible for damage to the wooden hulls of these boats to be easily repaired at the front lines by base force personnel. Five Elco Boats were manufactured in knock-down kit form and sent to Long Beach Boatworks for assembly on the West Coast as part of an experiment and as a proof of concept.

Higgins

of New Orleans, Louisiana produced 199 boats of the PT-71/PT-235, PT-265 and PT-625 classes. The Higgins boats had the same beam, full load displacement, engines, generators, shaft horsepower, trial speed, armament, and crew accommodation as the Elco boats. Many Higgins boats were sent to the Soviet Union and Great Britain at the beginning of the war, so many of the lower-numbered squadrons in the U.S. Navy were made up exclusively of Elcos. U.S. Navy PT boats were organized into motor torpedo boat squadrons. The first Higgins boats for the U.S. Navy were used in the battle for the Aleutian Islands as part of Squadrons 13 and 16, and others in the Mediterranean against the Germans. They were also used during the D-Day landings on 6 June 1944.
Even though only half as many Higgins boats were produced, far more survive than the more numerous Elco boats. Of the Elco boats, only three hulls were known to exist as of 2016.

Huckins Yacht Corporation

and his innovative Quadraconic hull design were latecomers to PT boat design. Not invited to participate in the original design competition, by late 1940, Huckins had a meeting with Captain James M. Irish, Chief of Design of BuShips, and offered to build a "planing seagoing hull" PT boat, on the condition the Navy loan Huckins engines and agree to look at the Huckins boat. In early July 1941, the Navy accepted PT-69. After obtaining excellent testing results at the Plywood Derby, the Navy awarded Huckins Yacht Corporation a contract in 1941 for 8 boats, and later added 10 more. The design was enlarged and modified to meet the new requirements. The first three of the new design were initially kept in the Jacksonville area for testing, resulting in several important modifications to the overall design. Huckins ended up building just two squadrons of PT boats during World War II. Five boats were assigned to Squadron 14 which was commissioned in early 1943; and ten boats assigned to Squadron 26 which was commissioned in mid 1943. They were assigned to specific outposts in the Panama Canal Zone, Miami, Florida, the Hawaiian Sea Frontier at Pearl Harbor and Midway, and a training center in Melville, Rhode Island.
Although not used in any other PT boat design, Huckins licensed the use of his patented Quadraconic hull in his PT boat construction. He also granted permission for Elco, Higgins, and the Philadelphia Navy Yard to use his patented laminated keel, which increased hull strength, although neither Elco nor Higgins ever chose to use it on their boats. Most probably due to the lateness in joining the PT boat program and unlike Elco and Higgins, the Huckins yard was never provided any government support to construct a larger facility prior to the war. The handcrafted Huckins PT was produced at their civilian facility at a speed of one per month. The success and ruggedness of the Huckins' 78-foot seagoing design is demonstrated by Squadron 26's constant ready-boat operations and Fleet torpedo boat training in the oceans around Midway and Hawaii during the last two years of the war.

Vosper and other types of PT boats

During World War II, Vospers of Great Britain arranged for several boatyards in the United States to build British-designed motor torpedo boats under license to help the war effort. The boatyards were located in Annapolis, City Island, Miami, and Los Angeles. 146 boats, armed with torpedoes, were built for Lend Lease, and exported to Allied powers such as Canada, Britain, Norway, and the Soviet Union. These boats were never used by the U.S. Navy, and only about 50 were used by the Royal Navy; most were passed to other countries.
In addition, the Canadian Power Boat Company produced four Scott-Paine designed PTs for the U.S. These were to be provided to the Dutch forces under Lend Lease, but were re-requisitioned to the USN as PT 368-371.

Construction

With accommodation for three officers and 14 enlisted men, the crew varied from 12 to 17, depending upon the number and type of weapons installed. Full-load displacement late in the war was 56 tons.
The hull shape of the Elco and Higgins PT boats were similar to the warped "planing hull" found in pleasure boats of the time : a sharp V at the bow softening to a flat bottom at the stern. A common characteristic of this type of warped hull is the "rooster tail" in the wake. Unlike the actual "planing hull" Huckins, which planed at 10-11 knots, the Elco and Higgins PT boats were intended to plane at higher speeds. The Elco, Higgins and Huckins companies used varying lightweight techniques of hull construction which included two layers of double diagonal mahogany planking utilizing a glue-impregnated cloth layer between inner and outer planks. These planks were held together by thousands of copper rivets and bronze screws. The overall result was an extremely light and strong hull which could be easily repaired at the front lines when battle damage was sustained. According to Robert McFarlane, the US Navy built the hulls of some PT boats partially from 3,000-year-old white cedar logs recovered from sphagnum bog in New Jersey.
: USS PT-167 is struck by an enemy torpedo, on 5 November 1943
As a testament to the strength of this type of construction, several PT boats withstood catastrophic battle damage and still remained afloat. For example, the forward half of future President John F. Kennedy's PT-109 stayed afloat for 12 hours after she was cut in half by the Japanese destroyer Amagiri. PT-323 was cut in half by a kamikaze aircraft on 10 December 1944 off Leyte, yet remained floating for several hours. PT-308 had her stern sheared off by a collision with PT-304 during a night mission in the Mediterranean on 9 March 1945 and yet returned to base for repairs. PT-167 was holed through the bow off Bougainville on 5 November 1943, by a torpedo which failed to detonate; the boat remained in action and was repaired the next day.
In 1943, an inquiry was held by the Navy to discuss planing, hull design, and fuel consumption issues. This resulted in the November 1943 Miami test trial between two Higgins and two Elco boats, but no major additional modifications were made before the end of the war. During the war, Elco came up with stepped hull designs which achieved significant increase in top speed. Higgins developed the small and fast Higgins Hellcat, which was a slight variation on their original hull form, but the Navy rejected them for full production due to increased fuel consumption and other considerations.
After the war, Lindsay Lord, who was stationed in Hawaii during the war, recorded the Navy's planing hull research and findings in the book Naval Architecture of Planing Hulls. This covers PT boat hull design and construction, and provides hull test data as well as detailed analysis of the various PT boat designs.

Armament

The primary anti-ship armament was two to four Mark 8 torpedoes, which weighed and contained a TNT warhead. These torpedoes were launched by Mark 18 steel torpedo tubes. Mark 8 torpedoes had a range of at. These torpedoes and tubes were replaced in mid-1943 by four lightweight Mark 13 torpedoes, which weighed and contained a Torpex-filled warhead. These torpedoes were carried on lightweight Mark 1 roll-off style torpedo launching racks. The Mk13 torpedo had a range of and a speed of.
PT boats were also well armed with numerous automatic weapons. Common to all US PT boats were the two twin M2.50 cal machine guns. Early PT boats mounted Dewandre plexiglas-enclosed hydraulically operated rotating turrets. Almost immediately after the attack on Pearl Harbor, the Dewandre turrets were replaced on the entire PT boat fleet with open ring twin mounts. The ring mount was designed by both Elco and Bell, and designated Mark 17 Twin 50 caliber aircraft mount. Part of the Mark 17 Mod 1 and Mod 2 ring mount consisted of the Bell Mark 9 twin cradle. Another automatic weapon commonly mounted on PT boats was the 20 mm Oerlikon cannon. On early series of boats, this cannon was mounted on the stern. Later in the war, several more of these 20 mm cannons were added amidships and on the forward deck.
Forward of the chart house of some early Elco boats were twin.30 cal Lewis machine guns on pedestal mounts. Beginning in mid-1943, some boats were fitted with one or two.30 cal Browning machine guns on the forward torpedo racks on pedestal mounts.
Occasionally, some front line PT boats received ad hoc up-fits at forward bases, where they mounted such weapons as 37mm aircraft cannons, rocket launchers, or mortars. When these weapons were found to be successful, they were incorporated onto the PT boats as original armament. One such field modification was made to Kennedy's PT-109, which was equipped with a single-shot Army M3 37mm anti-tank gun that her crew had commandeered; they removed the wheels and lashed it to 2x8 timbers placed on the bow only one night before she was lost. The larger punch of the 37mm round was desirable, but the crews looked for something that could fire faster than the single-shot army anti-tank weapon. Their answer was found in the 37mm Oldsmobile M4 aircraft automatic cannon cannibalized from crashed P-39 Airacobra fighter planes on Henderson Field, Guadalcanal. After having demonstrated its value on board PT boats, the M4 cannon was installed at the factory. The M4/M9 37mm auto cannon had a relatively high rate of fire and large magazine. These features made it highly desirable due to the PT boat's ever-increasing requirement for increased firepower to deal effectively with the Japanese Daihatsu-class barges, which were largely immune to torpedoes due to their shallow draft. By the war's end, most PTs had these weapons.
The installation of larger-bore cannons culminated in the fitting of the 40mm Bofors gun on the aft deck. Starting in mid-1943, the installation of this gun had an immediate positive effect on the firepower available from a PT boat. The Bofors cannon had a firing rate of 120 rounds/min and had a range of. This gun was served by a crew of 4 men, and was used against aircraft targets, as well as shore bombardment or enemy surface craft.

Gunboats

In the Solomon Islands in 1943, three PT boats, PT-59, PT-60, and PT-61, were converted into "PT gunboats" by stripping them of all original armament except the two twin.50 cal gun mounts, then adding two 40mm and four twin.50 cal mounts. Lieutenant Kennedy was the first commanding officer of PT-59 after its conversion. On 2 November 1943, PT-59 participated in the rescue of 40 to 50 Marines from Choiseul Island and a foundering landing craft which was under fire from Japanese soldiers on the beach.
Towards the end of the war, beginning in 1945, PTs received two eight-cell Mark 50 rocket launchers, launching spin-stabilized flat trajectory Mark 7 and/or Mark 10 rockets with a range of. These 16 rockets plus 16 reloads gave them as much firepower as a destroyer's guns. By war's end, the PT boat had more "firepower-per-ton" than any other vessel in the U.S. Navy.
PT boats also commonly carried between two and eight U.S. Navy Mark 6 depth charges in roll-off racks. Sometimes they were used as a last-ditch weapon to deter pursuing destroyers. The depth charge could be set to go off at, and by the time it exploded, the pursuing destroyer might be above it.
Additionally, a few PT boats were equipped to carry naval mines launched from mine racks, but these were not commonly used.

Engines

With the exception of the experimental PT boats, all U.S. PT boats were powered by three marine modified derivations of the Packard 3A-2500 V-12 liquid-cooled, gasoline-fueled aircraft engine. Improvements upon Packard's World War I Liberty L-12 2A engine, the successive "M" for "marine" designated 3M-2500, 4M-2500, and 5M-2500 generations all featured slight changes and more power. Their superchargers, intercoolers, dual magnetos, and two spark plugs per cylinder reflected their aircraft origins.
Packard's licensed manufacture of the famed Rolls-Royce Merlin aircraft engine alongside the marine 4M-2500 has long been a source of confusion. Only the British built PT-9 prototype boat brought from England for Elco to examine and copy featured a Merlin.
The 4M-2500 initially generated. It was subsequently upgraded in stages to, allowing a designed speed of. The 5M-2500 introduced in late 1945 had a larger supercharger, aftercooler, and increased power output of. It could push fully loaded boats at. However, subsequent additions of weaponry offset this potential increase in top speed.
Fuel consumption of any version of these engines was exceptionally heavy. A PT boat carried of 100 octane aviation fuel, enough for a 4M-2500 equipped boat to conduct a maximum 12-hour patrol. Some an hour were consumed at a cruising speed of, increasing to per hour at top speed. Hull fouling and engine wear could both decrease top speed and increase fuel consumption materially.

Service

PT boats operated in the southern, western, and northern Pacific, as well as in the Mediterranean Sea and the English Channel.

Early use

Originally conceived as anti-ship weapons, PT boats were publicly credited with sinking several Japanese warships during the period between December 1941 and the fall of the Philippines in May 1942. Attacking at night, PT boat crews may have sometimes failed to note a possible torpedo failure. Although the American Mark 8 torpedo did have problems with porpoising and circular runs, it could and did have success against common classes of targets. The Mark 3 and Mark 4 exploders were not subject to the same problems as the Mark 6 exploders on U.S. submarines' Mark 14 torpedoes. Introduction of the Mark 13 torpedo to PT boats in mid-1943 all but eliminated the early problems that PT boats had with their obsolete Mark 8s.

Night attacks

PTs would usually attack at night. The cockpits of PT boats were protected against small arms fire and splinters by armor plate. Direct hits from Japanese guns could and did result in catastrophic gasoline explosions with near-total crew loss. They feared attack by Japanese seaplanes, which were hard to detect even with radar, but which could easily spot the phosphorescent wake left by PT propellers. Bombing attacks killed and wounded crews even with near misses. There are several recorded instances of PT boats trading fire with friendly aircraft, a situation also familiar to U.S. submariners. Several PT boats were lost due to friendly fire from both Allied aircraft and destroyers. Enemy forces would use searchlights or seaplane-dropped flares to illuminate fleeing PT boats.
Initially, only a few boats were issued primitive radar sets. U.S. Navy PTs were eventually fitted with Raytheon SO radar, which had about a range. Having radar gave Navy PTs a distinct advantage in intercepting enemy supply barges and ships at night. As more PTs were fitted with dependable radar, they developed superior night-fighting tactics and used them to locate and destroy many enemy targets. During the Guadalcanal and Solomon Island campaigns in 1942–1943, the PT boats of Squadrons 2, 3, 5 and 6 would lie in wait to ambush a target from torpedo range, generally about.
, 1943
During some of these nighttime attacks, PT boat positions may have been given away by a flash of light caused by grease inside the black powder-actuated Mark 8 torpedo tubes catching fire during the launching sequence. In order to evade return fire from the enemy ships, the PT boat could deploy a smoke screen using stern-mounted generators. Starting in mid-1943, the old Mark 18 torpedo tubes and Mark 8 torpedoes were replaced. The new Mark 1 "roll-off" torpedo launcher rack effectively eliminated the telltale flash of light from burning grease, did not use any form of explosive to launch the torpedo, and weighed about less than the tubes.

Solomon Islands campaign

The effectiveness of PT boats in the Solomon Islands campaign, where there were numerous engagements between PTs and capital ships, as well as against Japanese shipborne resupply efforts dubbed "The Tokyo Express" operating in New Georgia Sound, was substantially undermined by defective Mark 8 torpedoes. The Japanese were initially cautious when operating their capital ships in areas known to have PT boats, knowing how dangerous their own Type 93 torpedoes were, and assumed the Americans had equally lethal weapons. The PT boats at Guadalcanal were given credit for several sinkings and successes against the vaunted Tokyo Express. In several engagements, the mere presence of PTs was sufficient to disrupt heavily escorted Japanese resupply activities at Guadalcanal. Afterwards, the PT mission in the Solomon Islands was deemed a success.

D-Day invasion

Some served during the Battle of Normandy. During the D-Day invasion, PTs patrolled the "Mason Line", forming a barrier against the German S-boats attacking the Allied landing forces. They also performed lifesaving and anti-shipping mine destruction missions during the invasion.

Barge attacks

Perhaps the most effective use of PTs was as "barge busters". Since both the Japanese in the New Guinea area and the Germans in the Mediterranean had lost numerous resupply vessels to Allied air power during daylight hours, each attempted to resupply their troop concentrations by using shallow draft barges at night in very shallow waters. The shallow depth meant Allied destroyers were unable to follow them due to the risk of running aground and the barges could be protected by an umbrella of shore batteries.
The efficiency of the PT boats at sinking the Japanese supply barges was considered a key reason that the Japanese had severe food, ammunition, and replacement problems during the New Guinea and Solomon Island campaigns, and made the PT boats prime targets for enemy aircraft. The use of PT boat torpedoes was ineffective against these sometimes heavily armed barges, since the minimum depth setting of the torpedo was about 10 feet and the barges drew only 5 feet.
To accomplish the task, PTs in the Mediterranean and the Pacific installed more and heavier guns which were able to sink the barges. One captured Japanese soldier's diary described their fear of PT boats by describing them as "the monster that roars, flaps its wings, and shoots torpedoes in all directions."
Though their primary mission continued to be attack on surface ships and craft, PT boats were also used effectively to lay mines and smoke screens, coordinate in air-sea rescue operations, rescue shipwreck survivors, destroy Japanese suicide boats, destroy floating mines, and carry out intelligence or raider operations.
After the war, American military interviews with captured veterans of the Imperial Japanese Navy, supplemented by the available partial Japanese war records, were unable to verify that all the PT boat sinking claims were valid. Like many other victory claims by all parties involved this unclear verification was due in part to the Japanese military's policies of destroying military records.

Repair training

In 1944, several Higgins boats were converted, releasing PT-59, PT-60, and PT-61 for transfer back home to the Motor Torpedo Boat Squadrons Training Center school in Melville, Rhode Island for use in training in hull repair techniques.

Supply

PT boats lacked a large capacity refrigerator to store sufficient quantities of perishable foods. While docked, PT boat squadrons were supported by PT boat tenders or base facilities which supplied boat crews with hot meals. As PT boats were usually located near the end of the supply chain, their crews proved resourceful in bartering with nearby ships or military units for supplies and using munitions to harvest their own fish.

Boats

Many PT boats became famous during and after World War II:
According to the book "At Close Quarters: PT Boats in the United States Navy" 99 of the 531 PT boats that served during World War II were lost to various causes.
At the end of the war, almost all surviving U.S. PT boats were disposed of shortly after V-J Day. Hundreds of boats were deliberately stripped of all useful equipment and then dragged up on the beach and burned. This was done to minimize the amount of upkeep the Navy would have to do, since wooden boats require much continuous maintenance, and they were not considered worth the effort. The boats also used a lot of high octane gasoline for their size, making them too expensive to operate for a peacetime navy. Much of this destruction occurred at PT Base 17, on Samar, Philippines, near Bobon Point.

Production boats

A few were cut up and destroyed between 1998 and 2008, leaving total of 12 PT boats, and 2 experimental PT boat hulls in various states of repair, surviving today in the U.S.:
;PT-48
PT-48 is possibly the last surviving Elco PT boat. In July 1942, PT-48 was assigned to MTBRON 3. This second Squadron 3 was the first to arrive in the Solomons and saw heavy engagement with the "Tokyo Express". PT 48 was one of the first 4 boats to arrive at Tulagi, on 12 October 1942. On the night of 13/14 October 1942, PT-48 engaged a Japanese destroyer at. This Squadron saw action in the Solomon Islands, Guadalcanal, and Funafuti. PT-48 is today in need of major restoration, after having been cut down to and used as a dinner cruise boat. Because of this boat's extensive combat history, having survived 22 months in the combat zone at Guadalcanal, a preservation group, "Fleet Obsolete" of Kingston, New York, acquired and transported it to Rondout Creek in 2008 for eventual repair.
;PT-305
One of two fully restored and operational PT boats and the only combat veteran of the two, PT-305 is a Higgins boat, assigned during the war to MTBRON-22, and saw action against the Germans in the Mediterranean Sea. Squadron 22 was operating with the British Royal Navy Coastal Forces, and saw action along the northwest coast of Italy and southern coast of France. In June 1945 the squadron was shipped to the U.S. for refitting and transfer to the Pacific, but the war ended while still in New York. PT-305 was cut down to for use as an oyster seed boat in Crisfield, Maryland. PT-305 was acquired by the Defenders of America Naval Museum, and then sold in May 2007 to the National World War II Museum in New Orleans. After a lengthy restoration PT-305 has been restored to a seaworthy, operational vessel. It was relaunched in March 2017, and the museum is booking rides on Lake Pontchartrain on Saturdays, or static tours other days of the week.
;PT-309
A Higgins, PT-309 was assigned during the war to MTBRON 22, and saw action against the Germans in the Mediterranean Sea. The squadron was operating under the British Coastal Forces, and saw action along the northwest coast of Italy and southern coast of France. In April 1945 the squadron was shipped to the U.S. for refitting and transfer to the Pacific, but the war ended while still in New York. Coincidentally, the PT-309, was named in honor of Frank Sinatra, with whom the boats' Commanding Officer met at a nightclub shortly before MTBRON 22 left New York for the Mediterranean Theatre. PT-309 is located at the National Museum of the Pacific War / Admiral Nimitz Museum in Fredericksburg, Texas, and was restored by the Defenders of America Naval Museum. PT-309 is restored in a static diorama display without engines installed. Her external restoration was completed by the Texas group in 2002, and is to a high standard.
;PT-459
PT-459 a Higgins boat, was assigned to MTBRON 30 on 15 February 1944 under the command of LCDR Robert L. Searles. MTBRON 30 saw action in the English Channel as part of the Invasion of Normandy. In late June 1945 the squadron was shipped to the U.S. for refitting and transfer to the Pacific, but the war ended while still in New York. After the war, the ex-PT459 was cut down to and highly modified into a sightseeing boat and fishing trawler. She was acquired by Fleet Obsolete in June 2008 and moved to Kingston, New York for possible restoration.
;PT-486
PT-486, an Elco boat, was placed in service on 2 December 1943. It was used in the training squadron MTBRON 4 in Melville, Rhode Island during World War II until it was placed out of service 16 January 1946. Along with PT-557, the vessel was purchased from BFM Industries by Capt. George C. Sinn of Wildwood Crest, NJ on 9 October 1951 for $1,015.00. The vessel was sold in 1952 to Otto Stocker who operated the "Sightseer" as an excursion vessel from Otten's Harbor in Wildwood, New Jersey. The business was later sold to Capt. Charles Schumann in the 1980s. He named the vessel Schumann's "Big Blue" and ran the business until 2002. Remarkably, the PT486 was sold to the son of the original owner, Capt. Ronald G. Sinn, who in 2012 sold the boat to "Fleet Obsolete" of Kingston NY. Plans are for restoring the vessel to recreate the World War II appearance.
;PT-615
PT-615, an Elco originally assigned to MTBRON 42, was commissioned after the war ended. PT-615 was returned to Elco after being sold and was heavily modified into a yacht, which was leased to actor Clark Gable. He named the boat Tarbaby VI, and used her through the 1950s. The boat was serviced and stored by Elco. She was sold several times, and moved to Kingston, NY for possible restoration.
;PT-617
PT-617 is an Elco boat located at the Battleship Cove Naval Museum in Fall River, Massachusetts. She was obtained from the backwaters of Florida and moved to its current location by JM "Boats" Newberry, the founder of PT Boats Inc. "Boats" along with the team at Battleship Cove Museum restored her during 1984–89, inside and out, at a cost of US$1 million. The boat is owned by PT Boats, Inc., a World War II PT veterans organization headquartered in Germantown, Tennessee.
The quality of the restoration was extremely high, and the boat is on display inside a weatherproof building, on blocks out of the water. She is available for public viewing, and has portions of her hull cut away to display the cramped interior of the crew's quarters. General visitors are not allowed inside the boat in order to help preserve her historic integrity.
;PT-657
PT-657, a Higgins boat, has been converted into a charter fishing boat. She is located in San Diego and is now named Malihini.
;PT-658
One of the best examples of a surviving Higgins boat is PT-658, one of two 100% authentically restored and operational U.S. Navy PT boats afloat today. Relaunched after hull restoration from 1995 to 2005, it is located at Pier 308, Vigor Shipyard in Portland, Oregon's Swan Island Lagoon. Maintained by an all volunteer group, it is powered by the three Packard V12 5M-2500 gas engines and includes all weapons, electronics, equipment and accessories restored to appear as they did the day the US Navy accepted the boat, July 31, 1945.
PT-658 was added to the National Register of Historic Places in 2012.
;PT-724
PT-724, a surviving Vosper built at the Annapolis Boat yard in Maryland, has been used as a yacht, and has since been acquired by the Liberty Aviation Museum to be restored back to original Vosper configuration.
;PT-728
PT-728, a surviving Vosper boat built under license at the Annapolis Boat Yard in Maryland, was restored in Key West, Florida. Her deck house was reconfigured to partially resemble an Elco instead of its original Vosper 70 ft configuration. PT-728 was acquired by Fleet Obsolete and moved to Kingston. There PT-728 allows up to 49 tourists the chance to ride on a "PT boat". This boat is the only U.S. Coast Guard regulation-approved PT boat licensed to take passengers for hire, and the only surviving U.S.-built Vosper design. In spring of 2012, PT-728 was acquired by the Liberty Aircraft Museum of Port Clinton, OH for further restoration.
;PT-766
PT-766 is an Elco boat that is a private yacht located in Washington D.C. She represents the final class of Elco's with significant updates to the superstructure and radar and was intended for MTBRON 44, but was cancelled due to the end of the war.
;PT-796
PT-796 is a Higgins. After the war ended PT-796 was used in the Key West/Miami area for experimental purposes. She was retired from service in the late 1950s. Shortly after her retirement from service, the PT-796 was used as a float during President John F. Kennedy's inaugural parade to represent PT-109, with the PT-109 hull number painted on the bow, and several of PT-109's surviving crew members manning the boat. Today, PT-796 is located at the Battleship Cove Naval Museum in Fall River, Massachusetts in a Quonset hut-style building, protected from the weather, and up on blocks. The boat is owned by PT Boats, Inc., a World War II PT veterans organization headquartered in Germantown, Tennessee.

Experimental boats

;PT-3
Two of the experimental PT-Boats also still survive, PT-3 in New Jersey and PT-8. PT-3 was designed by George Crouch and employed lightweight planing hull construction methods. A barrel-back, a unique double longitudinal planked lightweight hull on bent laminated oak framing, she was the "featherweight" of transportable PT boat design, but was later rejected by the Navy during trials in 1941 after being deemed too short to carry 4 torpedoes, as well as being able to only launch torpedoes stern first, which was a procedure considered too dangerous by BuOrd. PT-3 and PT-8 were both part of Motor Torpedo Boat Squadron 1 during the testing period. After testing was completed, PT-3 was transferred to Canada in April 1941 under lend-lease. PT-3 served with the RCAF Fleet as the RCAF Bras d'Or M413 based at Eastern Air Command in Halifax. She was transferred back to the United States in April 1945. Now located in a New Jersey boatyard in awaiting restoration.
;PT-8
PT-8 in Louisiana was built entirely from aluminum but did not pass the speed acceptance criteria for use as a PT boat for the U.S. Navy due to its weight. She was reclassified as a harbor patrol boat for the duration of the war.
;UK Vosper
The two Vosper boats in England were built by Vosper itself, and the first is in fairly good condition at Portsmouth. The second UK built boat is in private hands, floating on a canal north of London and being used as a private residence, though it is remarkably intact in its World War II configuration.

Exported PT boats

Ten Higgins boats were delivered in 1948 for use by the Argentine Navy during the late 1940s up until the late 1970s. All of these boats are now retired from naval use, with two still in civil use today as sightseeing boats on Mar del Plata: the Leonardo da Vinci and the Mar de la Plata. The other six boats are in various states of disrepair, sunk or scrapped.
The PT boat design was also exported after the end of the Second World War as an unarmed air-sea rescue launch for use by the South African Navy.

Movie stand-ins

The original 1962–66 McHale's Navy TV series used a Vosper design PT-694
Prior to starring in the television series this boat was purchased as war surplus by Howard Hughes and was used as the camera chase boat when the Spruce Goose made its only flight. The stern of the Vosper boat is visible in the footage of that event.
In John Ford's 1945 war film, They Were Expendable, two Elcos were used during filming along with four former MTBRON 14 78-foot Huckins.
For the 1962 movie PT-109, several USAF crash rescue boats were converted to resemble 80-foot Elcos when the few surviving boats were found to need too much work to make them seaworthy for use during the film.

General printed reference