Merlin III (RM 1S) Merlin III fitted with "universal" propeller shaft able to mount either de Havilland or Rotol propellers.Robertson 1973, p. 144. From late 1939, using 100-octane fuel and +12 psi boost (83 kPa gauge; or an absolute pressure of 184 kPa or 1.82 atm), the Merlin III developed at 3,000 rpm at ;Harvey-Bailey 1995, p. 155. using 87-octane fuel the power ratings were the same as the Merlin II. Used in the Defiant, Hurricane Mk.I, Spitfire Mk.I fighters, and Battle light bomber. First production Merlin III delivered 1 July 1938.
Merlin III (RM 1S) Merlin III fitted with "universal" propeller shaft able to mount either de Havilland or Rotol propellers.Robertson 1973, p. 144. From late 1939, using 100-octane fuel and +12 psi boost (83 kPa gauge; or an absolute pressure of 184 kPa or 1.82 atm), the Merlin III developed at 3,000 rpm at ;Harvey-Bailey 1995, p. 155. using 87-octane fuel the power ratings were the same as the Merlin II. Used in the Defiant, Hurricane Mk.I, Spitfire Mk.I fighters, and Battle light bomber. First production Merlin III delivered 1 July 1938.