British-built PT Boats

Discussion in 'Weapons, Technology & Equipment' started by Paul Michael Smith, Jun 12, 2019 at 9:17 AM.

  1. Can anyone confirm which engines were used in these vessels. I heard from someone a long time ago that Rolls Royce might have adapted some for use, though I'm guessing most used the American Packard V-12. Any information would be appreciated.
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  2. Orwell1984

    Orwell1984 Senior Member

    Information from pt on engines.

    PT Boat Info - PT Boat - Pakard V-12 Marine Engine

    As stated on the website the confusion seems to lie with the fact Packard built licenced Merlins for aircraft use. Additionally some sources list the PT-9 prototype boat brought over from the UK for examination as having a Merlin but this was a one-off and is not mentioned in the boats history here:
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  3. Dave55

    Dave55 Very Senior Member

  4. Spitfires of the Sea

    Spitfires of the Sea Stephen Fisher

    I'm assuming you mean Royal Navy Coastal Forces Motor Torpedo Boats and Motor Gun Boats? They had a variety of engines fitted into the 800 or so that were built during the war. There were a few marinised Rolls Royce Merlins, but these were few in number - probably only a dozen or so. As Packards became available they started to become the standard - from 1942 or so.
  5. Juha

    Juha Junior Member

    If you mean MTBs they were at first powered by 3 Isotta Fraschini 57-litre petrol engines each with 1200 shp. When Italy joined the war, that source dried out and at first they were substituted by less powerful Hall-Scott engines, eventually the Packard engines were fitted.
    Last edited: Jun 12, 2019 at 4:14 PM
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  6. Trux

    Trux 21 AG Patron

    My father used to say that his RAF rescue launch had three RR Merlin engines although he acknowledged that they were in fact Packard built. Packards were Merline modified to suit US production methods. The difference was probably only the different gauge used for the thread on bolts etc.

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  7. Juha

    Juha Junior Member

    Hello Mike
    Packard had also its own engines at least some of the 2500 series were marine versions, see Dave's post (#3). I don't know which of Packard engines were used in British MTBs/MGBs.
  8. Dave55

    Dave55 Very Senior Member

    Paper on Packard Merlin

    Attached Files:

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  9. Juha

    Juha Junior Member

    Did some old-fashioned research i.e. consulted some books
    The first British MTBs after the WWI (launched 1936-39) were powered by Napier petrol engines, the first MGBs (launched 1940) by RR engines. Then MTBs got the Isotta-Fraschinis, then lower powered Hall Scotts and then Pachards, were they license-build Merlins or Pachard own designs, a quick glance didn't give answer but maybe Packard's own design because no mention that they would have been license built Merlins. And Coastal Forces didn't get RR Merlins because RAF needed all of them so IMHO at least at first I doubt that it could get Pachard merlins either before a/c industry demands for Merlins were satisfied. MTB424-429 (launched 1944) had Sterling engines, all to Poland after completion. MGB 502, 503 and 509, Paxman diesels. And then the British oddies SGB 1 - 9 (Steam Gun Boat) Metrowick geared turbines
    Last edited: Jun 12, 2019 at 5:49 PM
  10. Spitfires of the Sea

    Spitfires of the Sea Stephen Fisher

    It's not so much the boat type, but the builder that affected the engines. British Power Boats' 1930s MTBs were equipped with a marinised Napier Lion engines (a modification made by Hubert Scott-Paine, the company's founder). He then marinised Rolls Royce Merlin engines for an experimental MTB. Unfortunately these were in short supply even before the war, and British Power Boat was only able to secure them for some boats being built, oddly, for foreign navies. As it happens, these boats were all requisitioned and converted to MGBs, so the Merlins ended up powering a few British boats. Scott-Paine instead went to Packard and, with his experience with Rolls Royce, convinced the company to modify the M2500 engine for use in British boats, as well as British Power Boat designs being built by Elco. Once ready, these engines equipped all the Coastal Forces boats built by British Power Boat.

    Vosper meanwhile were using the Admiralty's favoured supplier, Isotta-Fraschini. Inconveniently, this supply dried up when Italy declared war and Vosper were forced to reply on Hall Scott engines for their MTBs. As Packard's new engine became available,these were retrofitted, or installed in new build Vospers. The same Packard M2500 also went into the new Fairmile D MTBs and MGBs.

    There were other boat builders of course. Thornycroft used Isotta-Fraschini engines in some of their boats and later, their own Thornycroft engines in a small series of unsuccessful boats. They were only a small producer of MTBs in the Second World War though. White's of Cowes used Sterlings, but again, only in small numbers. Other small experimentation with different engines continued throughout the war.

    Altogether some 4,600 of Packard's M2500 engines were supplied to the UK during the war. This is separate to the Packard-built Merlin for aircraft. I can't imagine any of those ended up in boats as they'd require extensive modification, and the M2500 already fitted the bill.

    I suspect these may have been M2500s. Scott-Paine convinced Packard to incorporate a number of modifications he designed for the Rolls Royce marinised engines, including the gear box. But to the best of my knowledge, British Power Boat HSLs were powered by Napiers, and Vosper and Thornycroft boats by Thornycrofts. There were a few boats that came from the US and Canada with M2500 Packards, amongst other engines. Certainly possible that a few Merlins made their way onto HSLs though - or that some of the MGBs with Merlins were handed over to rescue duties.

    Here's some useful reading on the subject of Coastal Forces engine development through the war. Above is just a general outline that I've simplified massively - especially the politics!:

    Adrian Rance, 1989. Fast Boats & Flying Boats. Ensign Publications.
    The biography of Hubert Scott-Paine, the founder of British Power Boat Company and one of the leaders in short MTB and MGB design.

    John Lambert & Al Ross, 1990. Allied Coastal Forces of World War II Volume 1: Fairmile Designs & US Submarine Chasers. Conway Maritime Press.
    A detailed technical history of Fairmile’s boats and their US equivalents.

    John Lambert & Al Ross, 1993. Allied Coastal Forces of World War II Volume 2: Vosper MTBs & US ELCOs. Conway Maritime Press.
    A detailed technical history of Vosper and Elco boats.
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  11. Some excellent information. Many thanks. One of the reasons for my question was that my father reckoned that after the war the lifeboat service used some of these vessels. Is this likely to have been the case?
  12. Spitfires of the Sea

    Spitfires of the Sea Stephen Fisher

    Not something I've heard before. Looking through the Vosper lists I don't see anything that specifies the RNLI purchased any boats, but there are a lot that just say 'sold' so it's possible. I'm not convinced it would have happened in large numbers though - I've never seen a picture of a Coastal Forces boat in post-war RNLI service, and they weren't really that ideal as a boat type for that work. Large numbers of RAF Air Sea Rescue boats remained in service though.
  13. Don Juan

    Don Juan Well-Known Member

    British MTB's and MGB's are one of my interests, and a while ago I did a tot-up of the production totals as below:

    MTB - Short


    60 ft. Type - 6 (ex-Royal Norwegian Navy)
    70 ft. Type - 12 (6 ex-Greek Navy)
    71 ft. Type - 104 (+ 64 U.S. production)
    73 ft. Type - 32

    J.S. White

    70ft. Type - 2 (ex-Polish Navy, became MGB's)
    73ft. Type - 20 (Vosper/White hybrids) + 18 Vospers


    55 ft. Type - 14 (WWI-style CMB's, ex-Finnish, Chinese, Philippine Navies)
    75 ft. Type - 11

    British Power Boats

    60 ft. Type - 19

    MGB - Short

    British Power Boats

    63 ft. Type - 4 (ex-Norwegian Navy, originally MA/SB's) +2 to Polish Navy
    70 ft. Type - 35 (Originally MA/SB's, 14 ex-French Navy, 1 ex-Royal Netherlands Navy)
    71' 6" Type - 96 (Reclassified as MTB, Late '43)

    MGB - Long


    Type C - 24 (Interim design)
    Type D - 229 (Reclassified as MTB, Late '43)

    Camper & Nicholson

    117 ft. Type - 17 (Reclassified as MTB, Late '43)


    British Power Boats

    60 ft. Type MA/SB - 5 (Same hull as 60ft. MTB)
    63 ft. Type MA/SB - 18


    ASR - RAF


    73 ft. Type HSL - 15 (Shortened Fairmile D)

    British Power Boats

    64 ft. Type HSL - 22 (Stretched 60ft. MTB)
    63 ft. Type HSL - 69 (Same hull as MA/SB)
    68 ft. Type HSL - 90


    67 ft. Type HSL - 104


    65 ft. Type HSL - 1 (Prototype)
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  14. Roy Martin

    Roy Martin Senior Member

    Fairmile Design Vessels built at Clausentum Yard
    Risdon Beazley built 22 Fairmiles; they were the lead yard in the south and fourth nation-wide. Risdon Beazley's average building times were: "B" type, 9 boats, 21 weeks (24.8 weeks), "C" type, 1 boat, 27 weeks (29 weeks) and "D" type, 12 boats, 33 weeks (43.3weeks) - top yard. (National averages in brackets). [1]
    B Type
    204 ML 27.02.41 To Burma RNVR 1.11.45, for disposal 1946
    208 ML 12.03.41 RNN 12.3.41, for disposal 10.45
    265 ML 30.05.41 Lost by fire, Freetown 1.7.44
    338 ML 28.09.41 Became ML2338, sold 17.12.56
    347 ML 17.10.41 Sold 1.47 = yacht "Venturer". Still in operation 2005
    467 ML 06.12.41 For disposal 10.45
    468 ML 29.01.42 For disposal 9.45
    498 ML 15.04.42 "Sea Eagle" 1955, Derry SCC 11.57, sold 9.63
    499 ML 00.05.42 Sold 4.3.46

    C type
    327 MGB 22.08.41 For disposal 10.45

    D type
    646 MTB 19.11.42 For disposal 8.45
    649 MGB 07.01.43 For disposal 9.45. Mediterranean
    676 MTB 13.05.43 To RAF 6.45 = LRRC024
    680 MTB 00.04.43 To RAF 6.45 = LRRC028
    705 MTB 07.08.43 Mined 23.03.45 in the Adriatic
    706 MTB 00.10.43 For disposal 9.45 to 7.46 Mediterranean
    738 MTB 15.12.43 To SCC Ipswich, sold 25.04.58
    744 MTB 00.03.43 RCN 3.44 - 5.44, to RAF 1945 = LRRC040
    772 MTB 12.07.44 To SCC Chelsea 1.46, sold 2
    789 MTB 17.10.44 Lost 14.02.45 by fire and explosion, Ostend
    5013 MTB 00.03.45 MTB3053 49, MASB3053 53, SCC 57, sold 69
    5019 MTB 13.04.45 To RAF 4.45 = LRRC011

    Others were built on the Itchen, by Southampton Steam Joinery
    [1] HSL (Harbour service launches) 441130, 441131, 441136, 441137, 441142, 441143, 441152, 441153, 441160, 441161. And smaller boats of which Cerf III may be the only survivor. This boat was built by Risdon Beazley in 1945, as boat no. 45772, a 36ft HL(P) Harbour Launch (Philip Simons – Lloyd’s Register–Fairplay). Mr Swain, who worked in the yard throughout the war says that " after the Fairmiles they built six small launches for the RN"
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  15. Roy Martin

    Roy Martin Senior Member

    The British continued to fly small cargoes out, but it was obvious to Binney that the only way to obtain enough ball bearings was to transport them by sea. His new plan involved using modified fast Motor Launches. After some deliberation the Admiralty made five diesel powered gun boats available for the work. These had been part of an order of eight destined for the Turkish Navy. Three were handed over to Camper and Nicholson for conversion and the other two went to the yard of Amos and Smith in Hull. Everything forward of the engine room was stripped out to make a hold in which forty tons of ball bearings could be stowed, and the bridge structure and accommodation were substantially altered. The boats had a maximum cruise speed of twenty knots, with a range of 1,200 miles at seventeen knots.
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