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Welcome to, an Elco 80' PT boat resource site
Elco PT Boat Outboard Profile Plan

This website is now sponsored by (hosts of web sites, applications, databases, E-mail, and groupware systems), and mirrored at through (Graphic Dimensions, Inc., marketing tools and technical data for art and marketing services). Thanks Tom and Dick!

Dick Washichek, webmaster at's forum and owner of Graphic Dimensions, has went through the expense of having microfilm rolls of Elco drawings scanned in and has made them available to the public. It is an amazing collection, details and ordering instructions can be found here: Dick also has another collection featuring content on Higgins 78 PT boats, Bath Iron Works PT 810, Elco 70 PT & PTC boats, Elco V-Drive, and a Packard Operating Manual available here: I now use these drawings extensively in my work, they have helped greatly. Get them while available. The original microfilm was supplied by author Al Ross. Thanks guys!

Rare drawings for the 21" Above Water Torpedo Tube Mark 18 Mod 1 and Mod 5, graciously provided from the collection of Al Ross:


2011 October 15 update: Helmsman's rubber mat and platform added. See the Helm page.

2011 October 9 update: Helm updated to Elco drawings. See the Helm page.

2011 October 5 update: Forward turret updated to Elco drawings and aft turret added. Turret step updated. See the Turrets page.

2011 June 6 update: Updated the list of drawings on Dick's Elco DVD.

2011 April 30 update: Additions and corrections made to the Manufacturers page.

2010 September 28 update: Bridge control panel drawing updated to Elco drawings. Separate drawings, showing changes, added. See the Controls page.

2010 September 14 update: Packard engine data added to the Specs page. Data was obtained from a manual available on Dick's 2nd DVD, see above for ordering.

2010 April 10 update: Deck construction table added to the Hull page to show which boats had planked decks and which boats had plywood decks.

2010 March 22 update: Turret step, as found on the side of the chart house and day room, added to the Turrets page.

2010 March 21 update: Deck Hatch page added. Deck hatch hold open device drawing moved from Hull page to the Deck Hatch page and the latch raised slightly to match hatch. Deck Ventilator and Dead Lights drawings moved from Hull page to their own pages.

2010 March 1 update: Specs page cleaned up a bit, added camber information, and fuel tank capacity corrected.

2010 February 19 update: Deck hatch hold open device added to the Hull page.

2010 February 7 update: Deck dead light placement and construction added. Deck beam dimension table added. See the Hull page.

2010 January 6 update: Deck vent plan updated to Elco plan specs, on the Hull page.

2009 October 1 update: A 5 view of the .50 cal. Mark 9 carriage added. Jerry Gilmartin supplied me with some measurements from an actual carriage on PT 658, thanks Jerry!

2009 September 29 update: Redrawn forward turret added.


This is a resource site by Jeff Davidson for the building details of an Elco 80' World War II Motor Torpedo Boat (MTB) / Patrol Torpedo (PT) boat with leanings towards a 109 to 138 boat operating in the Pacific theater. The dimensional images found here are to help modelers create an accurate tribute to the boats and the men who sometimes gave up their lives serving on them, and to help preserve their history. They represent a best effort on my part, please confirm dimensions given here for yourself if errors cannot be tolerated. Images are for non-commercial personal use only, please obtain permission for any other use. I can be contacted through elconaut at comcast dot net.

Number ranges for boats of this class, listed by production order, are 103-196, 314-367, 372-383, 546-563, 486-545, 731-760, and 565-624. There were quite a few minor and major changes made to them including during production ranges. Depending on available resources I'll try to include as many changes as I can. Please point out any errors you may find. Misinformation about PT boats is fairly common and something I don't want to be guilty of spreading.

While this site concentrates on the physical aspects of the PT boat, be sure to read the accounts on the veterans stories page and check other websites on the Links page to learn the stories of the men who served on them.

If you have, or know someone that has, any PT related images or items that you or they would like to donate please contact They are dedicated to the preservation of all things PT. Even items like water damaged images can be valuable to history. I would also be grateful for scans of photos or manuals.

PT Boat Background

Japanese Planning Pearl Harbor
Japanese Planning Pearl Harbor

Patrol Torpedo boats were built during a war that changed the way of life for Americans virtually overnight. The population was thrust willingly into a role of background support for the troops fighting overseas. Both had an iron will, given by Pearl Harbor, to do what was needed to defend their country. Both did without where they could so that resources could be directed to the war effort. Rationing was in effect, the motto was: Use it all; Wear it out; Make it do; or Go without. Victory gardens were planted to help ease food shortages and its transportation load. Many manufacturers changed production lines, for example a can factory before the war now made depth charges. Meat, sugar, butter, coffee, and gasoline were some of the items rationed. The average driver was allocated 3 gallons of gasoline per week. The Civil Air Patrol was formed to help guard coastlines.

Wise words from the Smith Corp.
WW2 Poster Production Or Destruction Smith Corp

They were built almost entirely of wood. Raw materials were in short supply, especially those imported from regions under the cloud of war such as rubber and high demand materials like metals. One resource that America had plenty of at the start of the war was wood and they used it to best advantage in the construction of PT boats. Although it didn't grow in the US, their Mexican friends supplied them with much of the mahogany used throughout the boat as well as many other resources. And they still help, they were one of the first to send aid after hurricane Katrina hit.

Packard V12, 4M-2500
PT Boat Packard 4M-2500
Besides being constructed of wood, the boats were relatively small and thus were not well received by many commanders used to having tons of steel under them. But it did not take long to change the perception of weakness that this created. With 3 supercharged Packard V-12 engines developing a total of 3,600 (4,500 by wars end) horsepower, they were quick, maneuverable, had a shallow draft, and were heavily armed. Roaming mostly at night they soon became the bane of the enemies war and supply craft, particularly in the Pacific Theater. They were grouped in squadrons, or RON's, that usually worked together patrolling inshore areas too shallow for warships with deeper drafts.

I've seen questions about their true effectiveness but the Japanese had no doubts. From a captured report dated December 6th 1943:
Since the beginning of the operation to take the island base of Guadalcanal in August 1942, the enemy has used PT boats aggressively. On their account our naval ships have had many a bitter pill to swallow. One destroyer and two submarines, for example, were attacked by them and sunk. Also, there are many examples of their having rendered the transport of supplies exceptionally difficult.

"They Were Expendable" still, M1917A1 "doughboy" helmet was replaced
between 1941-42 with M-1 "steel pot" type. "Zero" is actually a T-6 Texan.
.50 cal AA fire
PT boats were initially intended to torpedo capital Japanese ships, using the speed of the three Packards and its small size as advantages. The first eighty foot boats were armed with two twin Browning .50 caliber M2 aircraft machine guns and an Oerlikon 20mm Mark 4 cannon to use against enemy aircraft. They soon found more uses for the guns than just for anti-aircraft fire. One of their main targets became other shallow drafted vessels, namely Japanese troop and supply barges. These fed their many positions amongst the islands that made Allied advancement costly and difficult. When they could, unescorted barges would hug the shallow island coastlines to be under the protection of any shore batteries present and to avoid larger enemy vessels. But that didn't stop the PT boats that were able to go in after them. They were very successful at this, even with their torpedoes being useless on the shallow drafted barges. With the enemies resources cut off, Allied troops could hop over well entrenched enemy held islands without fear of reprisal although when approached these stranded men still fought on with a grim resolve. In some cases even after the war was over, usually because they hadn't heard the news. WWII Marshall Island Emaciated Japanese Soldiers September 1945

The Allies priority was to stop Hitler so supplies could be scarce in the Pacific Theater. Pacific crews became adept at flexibility. Sometimes whatever the crews could scrounge up ended up on the decks. Along with changes made by the Navy, an individual boat could look quite different at different time periods. As the war went on, changes that proved especially effective were used on new boats coming from the factory.

37mm Anti-Tank Gun M3
37mm Anti-Tank Gun
Commonly installed were 37mm and 40mm cannons, rocket launchers, mortars, even bazookas and captured Japanese weapons were used. For example, by August 1st 1943 the 109 had mounted or was in the middle of mounting a M3 37mm single shot anti-tank cannon they had "found" onto the foredeck (a later 37mm widely used on PT's was an Oldsmobile M4 or M9 automatic cannon, sometimes salvaged from P39 Aircobras). Although there is no record of it ever being fired, it did end up helping save lives.

Update: Geary Sims of let me know that the 37mm on the 109 was ordnance supplied and an official install that hadn't happened yet. The crew lashed the gun to the deck because leaving it on the dock while on patrol was not a good idea. Per Geary:

Reference the 37mm gun: Doing extensive research on PT 108 which also had the same 37mm gun, I found there are some myths. One, the 37mm anti-tank wasn't found, in fact there were 8 to 10 boats that had/were to have this mounting. It was an experimental mounting to see if the 37mm gun was effective against the Daihatsu barges. The guns came from and were mounted by members of the US Army 25th Infantry Division. From conversations with Dick Keresey and some of the 108 crew, Kennedy may have been the one who came up with the idea for the mounting.

Secondly, the newer mountings were not salvaged from P-39's. They were adapted by the Navy and the Elco plant to fit the PT Boats. The 108 received one plus the roll-off torpedoes.

The 109 was slated for the mounting of the 37mm on her return from that mission. That is why she had the lumber lashed to the deck. Didn't want to leave on the dock for it might not be there when they got back.

Thanks Geary! Geary also let me know to be careful with references since some photos were doctored to remove top secret equipment like radar masts, and misinformation was also spread.

The operation on the night the 109 met her fate is known as The Battle of Blackett Strait. It had been a confusing night with sporadic action, poor visibility, poor communications, and a questionable plan of attack. PT 109 was on patrol with the 162, part of a group of 15 boats going after four Japanese destroyers returning from a resupply run. With orders given for all boats that had expended their torpedoes to return to base, eleven had left including the only four with the newly installed radar. The thirteen men of the 109 found themselves creeping blindly on one engine searching for the enemy that they knew was close.

You may be wondering why the crew put themselves into a position of delayed response by shutting down the outboard engines with the enemy close. It was because of the poor visibility, and the luminescence of the Pacific's waters when stirred by the props made them almost as good of a target as they were during the day.

At about 0230 on the 2nd, a Japanese Fubuki class destroyer, the Amagiri, loomed up from the darkness bearing straight at the 109. Mistaken at first for another PT, it hit the 109 in front of the forward starboard torpedo tube and sliced her to between the center and starboard engines. It took 10 seconds to go from a quiet, albeit tense, night to being thrown into dark gasoline soaked waters with a huge enemy ship churning through them. Gasoline from the ruptured tanks burst into flames and burned two men, one of them badly. Two men were never seen again. Marney, manning the forward turret, and Kirksey, whose position at the time of the accident is unknown.

Luckily for the survivors, the Amagiri was traveling at about 40 knots and carried the bulk of the burning gas away with her wake. After burning for 15 minutes or so, the fire went out and the remaining crew went back to what was left of the 109, the bow section. They saw neither the 162 or the Amagiri again that night.

From a 22 August 1943 official report
PT 109 Sinking Report

The men clung to the still floating, but slowly sinking, remains until 1400 the next day. A 2x8 piece of wood that was being used as part of the 37mm mount served as a float for two of the crew with poor swimming skills. Be sure to read the whole story, Lt. Kennedy showed true courage in the rescuing of the badly burnt crew member and in his subsequent night swims in shark infested waters whilst trying to effect their rescue. Check here for a great story about the action that night by the captain of the 105, Dick Keresey. Check here for an official report on the sinking.

According to the captured Japanese documents, the sinking of the 109 was not an accident:
While the Amagiri (DD) was proceeding in Vella Bay on a reinforcement mission to Kolombangara on 2 August 1943, it detected an enemy PT boat close aboard and sank it by ramming.

Torpedo Tube - Early Boats
PT Boat Torpedo Tube
During the early part of the war the namesake weapon of these boats, the torpedo, was marginally effective at best. They would run too deep, explode early, or not explode at all. Since PT boats in the Pacific Theater operated mostly at night it was hard to tell misses from misfires so it took a while to figure out that the problem was the torpedo itself. Submarines relied on some of the same torpedo models and had similar results but the situation was not resolved for a good while. See this site for details. Also, the original torpedo tubes used by PT boats to launch them were very heavy, and the charge used for firing them created a visible flash. Later production had lightweight roll-off racks installed that were also retrofitted to earlier boats.
Elco 80' Construction
Elco PT Boat Construction
The Electric Launch Company was incorporated in 1892 and built electric powered pleasure craft. During World War I they built sub chasers for the British Admiralty, and then PT boats in WW II under the Elco Naval Division. After WW II they merged with sister company Electric Boat to form General Dynamics which decided to sell this division off in 1949. The old Elco plant in Bayonne N.J., then known as Electro Dynamic Motor Company, was destroyed by a fire on April 20th 1963. Another fire in 2002 finished the site off. The land had already been bought by developers when this happened so it was doomed anyway. Residential buildings were built. A boat lifting crane that survived the fires was restored in honor of Elco's contribution to the community and resides at a local park.

Elco used a technique of building the hull upside down then flipping it over for topsides construction. It wouldn't be practical for larger vessels but it was an efficient, and easier on the employees, method for this craft especially with the double planked hull. They were designed with modularity in mind for speed and efficiency of construction, "kitting" for assembly elsewhere, and for quick repairs. Laminating pieces requiring high strength, like engine bearers, allowed for strength without excess weight. Two straight beams called coamings run the length of the chart house, day room, and engine hatch, and are integral to the hull. These beams add strength and help seal water out since they rise up from the deck about 5 5/8". The top outsides are milled for a small amount of overlap with the plywood siding of the houses. A hatch in the chart house roof allows access to the fresh water tank located under removable floor sections. The day room roof and floor are also removable for access to the fuel tanks. Over 400,000 screws were used per boat.

Partial Elco 80' plan A-922, available at
Elco PT Boat Plan Section
Elco produced PT boats quickly and with a high degree of craftsmanship. Although one of the PT boats nicknames was "plywood coffin", and plywood was widely used, other woods also had their place depending on their properties and availability. The image to the left is a partial of a Type Sections plan dated 14th Oct. 1941 showing some of the different woods used.

Many structural elements were made of mahogany because of its rot resistance, strength to weight, workability, and ability to take a hit without splintering as badly as other woods. Splintering had long been a problem on wooden war vessels, it is where the oath "shiver me timbers" comes from. Cannon and gun fire would shiver, literally "shatter" or "splinter", the vessels timbers causing injury to the crew as well as to the sails and rigging. The entire hull was planked with a diagonally laid layer of mahogany, then a layer of glued canvas ironed flat, then another layer of mahogany laid at right angles to the first layer.

A testament to the strength of these hulls was when PT 167 had a Japanese Kate's torpedo punch right through the side of her bow and continue out the other side without exploding, The tail section was left in the crew's head which was rather fitting. Not only did the 167 make it back to base (the same can't be said of the Kate since it hit the 167's antenna and crashed into the sea), she carried injured crew from an LCI (landing craft infantry) back with her. A more brittle wood might have shattered bad enough to sink her or been hard enough to explode the warhead. There's a good picture of the damage in the book US PT Boats of WW2. Concerning the pilot of the Kate flying so low, he probably knew the PT was too shallow drafted to set the torpedo off so he was trying to skip the fish off the water and catch the boat on the fly, or he did exactly what he was trying to do with the direct hit.

To purchase PT boat plans, photographs, and more go to If you are building a Higgins boat, check out this Louisiana library site for many online plans.


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