Rolls Royce Merlin Variants

This is an incomplete list of representative Merlin variants. Engines of the same power output were typically assigned different model numbers based on supercharger or propeller gear ratios, differences in cooling system or carburettors, engine block construction, or arrangement of engine controls. All Merlin engines were "right hand tractor", i.e. propeller rotated to the right viewed from rear, unless otherwise noted.

  • Merlin II or III:
    1,030 hp (775 kW) at 3,000 rpm at 5,500 ft (1,680 m). Merlin III fitted with "universal" propeller shaft able to be fitted with de Havilland or Rotol propellers. With 100 Octane fuel and increased (+12lb/sq.in) Boost: 1,310 hp (977 kW) at 3,000 rpm at 12,250 ft (3,730 m) (Merlin III); used in Spitfire Mk.I and Hurricane Mk.I fighters, the Boulton Paul Defiant, and Fairey Battle.
  • Merlin X:
    1,130 hp (840 kW) at 3,000 rpm at 5,250 ft (1,525 m); used in Halifax Mk.I, Wellington Mk.II, and Whitley Mk.V bombers.
  • Merlin XII:
    fitted to Spitfire Mk. II.
  • Merlin XX:
    1,480 hp (1,105 kW) at 3,000 rpm at 6,000 ft (1,830 m); used in Hurricane Mk.II and Beaufighter Mk.II fighters, Halifax Mk.II and Lancaster Mk.I bombers.
  • Merlin 32:
    1,645 hp (1,230 kW) at 3,000 rpm at 2,500 ft (760 m); used in Barracuda Mk.II bomber.
  • Merlin 45:
    1,515 hp (1,130 kW) at 3,000 rpm at 11,000 ft (3,353 m); used in Spitfire Mk.V.
  • Merlin 46:
    1,415 hp (1,055 kW) at 3,000 rpm at 14,000 ft (4,270 m); high-altitude version used in Spitfire PR.Mk.IV and PR.Mk.VII
  • Merlin 50.M:
    1,585 hp (1,182 kW) at 3,000 rpm at 2,750 ft (838 m); Low altitude version with supercharger impeller "cropped" to 9.5 inches (240 mm) in diameter. Permitted boost was +18 lb/sq.in. instead of +16 lb/sq.in. as on a normal Merlin 50 engine. A "negative g" carburettor was fitted.
  • Merlin 61:
    fitted with a new two-speed two-stage supercharger providing 1,565 hp (1,170 kW) at 3,000 rpm at 12,250 ft (3,740 m), and 1,390 hp (1,035 kW) at 3,000 rpm 23,500 ft (7,170 m); high-altitude version used in Spitfire Mk.IX, and PR.Mk.XI
  • Merlin 76 & 77:
    1,233 hp (920 kW); used in the Westland Welkin high-altitude fighter and some later Spitfire and Mosquito variants. Fitted with a two-speed, two-stage supercharger and a Bendix-Stromberg carburettor. The odd-numbered mark drove a blower for pressurising the cockpit.
  • Merlin 130 & 131:
    2,070 hp (1,543 kW); redesigned "slimline" versions made for the de Havilland Hornet. Engine modified to decrease frontal area to minimum and was first Merlin series to use down-draught induction systems. Coolant pump moved from the bottom of the engine to the starboard side. Two -speed, two-stage supercharger and S.U Injection carburettor. Maximum Boost was 25 lb (2,053mm Hg). The Merlin 131 had an additional idler gear in the reduction gear casing allowing "reverse" (left hand tractor) rotation. Merlin 130 was fitted in starboard nacelle, Merlin 131 in port on production Hornets.
  • Merlin 133 & 134:
    2,030 hp (1,514 kW); Derated variants of 130/131 used in Sea Hornet F. Mk. 20, N.F. Mk. 21 and P.R. Mk. 22. Maximum Boost was lowered to 18 lb (1,691 Hg).
  • Merlin 266:
    the prefix 2 indicates built by Packard, otherwise as Merlin 66, optimised for low-altitude operation. Fitted to the Spitfire Mk. XVI.
Rolls Royce Merlin Variants
Variant Take-off Power Application Notes
Merlin I 890hp at 2850 rpm Battle I First production Merlin; 172 built. Merlin I through III used 100% glycol coolant.
Merlin II 880hp at 3000 rpm Spitfire I, Defiant I, Hurricane I, Sea Hurricane I, Battle I  
Merlin III 880hp at 3000 rpm Spitfire I, Defiant I, Hurricane I, Sea Hurricane I, Battle I 1310 hp at 9,000 ft, +12 lb/sq.in, with 100 octane fuel (5 minute limit)
Merlin VIII 1080hp at 3000rpm Fulmar I 1275hp 100 octane
Merlin X 1075hp at 3000rpm Halifax I, Wellington II, Whitley V and VII  
Merlin XII 1175hp at 3000rpm Spitfire II Coffman cartridge starter. First version of Merlin to use 30/70% glycol/water coolant.
Merlin XX 1280hp at 3000rpm Beaufighter II, Defiant II, Halifax II and V, Hurricane II and IV, Lancaster I and III, Spitfire III  
Merlin 21 1280hp at 3000rpm Mosquito I, II, III, IV and VI  
Merlin 22 1280hp at 3000rpm Lancaster I and III, York I  
Merlin 23 1390hp at 3000rpm Mosquito I, II, IV, VI, XII and XIII  
Merlin 24 1620hp at 3000rpm Lancaster I and VII, York I, Handley Page Halifax II  
Merlin 25 1620hp at 3000rpm Mosquito VI and XIX
Merlin 27 1620hp at 3000rpm Hurricane IV  
Merlin 28 1300hp at 3000rpm Lancaster I and III, Kittyhawk II (P-40F) Built by Packard as the V-1650-1
Merlin 29 1300hp at 3000rpm Hurricane (Canadian-built), Kittyhawk II (P-40F). Built by Packard as the V-1650-1, splined airscrew shaft
Merlin 30 1300hp at 3000rpm Barracuda I, Fulmar II  
Merlin 31 1300hp at 3000rpm Mosquito XX (Canadian), Mosquito 40 (Australia), Kitthawk II (P-40F and L) Built by Packard as the V-1650-1
Merlin 32 1600hp at 3000rpm Barracuda II, Seafire II, Hurricane V, Spitfire PR Mk. XIII  
Merlin 33 1390hp at 3000rpm Mosquito XX (Canadian), Mosquito 40 (Australia) Packard-built Merlin 23
Merlin 38 1390hp at 3000rpm Lancaster I and II Packard built Merlin 24
Merlin 45 1185hp at 3000rpm Spitfire V, PR Mk. IG (later redesignated PR.VII), PR Mk IV, Seafire IB, IIC  
Merlin 45M 1230hp at 3000rpm Spitfire LF.V  
Merlin 46 1100hp at 3000rpm Spitfire V, PR.IV and VII, Seafire IB, IIC  
Merlin 47 1415hp at 3000rpm Spitfire HF.VI high-altitude intercepter Fitted with a cabin pressure blower.
Merlin 50 1185hp at 3000rpm Spitfire V  
Merlin 50M 1230hp at 3000rpm Spitfire LF Mk.V  
Merlin 55 1185hp at 3000rpm Spitfire V, Seafire III  
Merlin 55M 1230hp at 3000rpm Spitfire LF.V, Seafire III  
Merlin 60 1165hp at 3000rpm Wellington VI  
Merlin 61 1290hp at 3000rpm Spitfire F Mk. IX, PR Mk. XI Two-stage supercharger fitted
Merlin 62 1165hp at 3000rpm Wellington VI  
Merlin 63 1290hp at 3000rpm Spitfire VIII, IX, PR.XI Replaced Merlin 61.
Merlin 63A 1710hp at 3000rpm Spitfire PR.XI  
Merlin 64 1290hp at 3000rpm Spitfire F Mk. VII Cabin pressure blower
Merlin 66 1315hp at 3000rpm Spitfire LF.VIII, LF Mk.IX Bendix-Stromberg anti-g carburettor.
Merlin 67 1315hp at 3000rpm    
Merlin 68 1400hp at 3000rpm Mustang III (P-51B and C) Packard-built as V-1650-3
Merlin 69 1490hp at 3000rpm Mustang III and IV (P-51C,D,F and K) Packard-built as V-1650-7
Merlin 70 1250hp at 3000rpm Spitfire HF.VIII Bendix-Stromberg anti-g carburettor.
Merlin 71 1250hp at 3000rpm Spitfire HF.VII Cabin pressure blower, Bendix-Stromberg anti-g carburettor.
Merlin 72 1290hp at 3000rpm Mosquito PR.IX, B.IX, XVI, 30, Welkin I  
Merlin 73 1290hp at 3000rpm Mosquito XVI, Welkin I  
Merlin 76 1250hp at 3000rpm Mosquito XVI, 30, Welkin I Same as Merlin 72 with a cabin pressure blower
Merlin 77 1250hp at 3000rpm Mosquito XVI, Welkin I, Spitfire PR.X Same as Merlin 73 with a cabin pressure blower
Merlin 85 1635hp at 3000rpm Lancaster VI, Lincoln I  
Merlin 224 1620hp at 3000rpm Lancaster I and III Packard-built Merlin 24
Merlin 225 1620hp at 3000rpm Mosquito 25 and 26 Packard-built Merlin 25
Merlin 266 1315hp at 3000rpm Spitfire LF. Mk. XVI Packard-built Merlin 66