Received his professional training at Bristol and in Paris. He entered the Navy as a Surgeon in 1859, became Staff Surgeon in 1871, Fleet Surgeon in 1882, and retired with the rank of Deputy Inspector-General of Hospitals and Fleets in the same year. From 1868-1865 he was Assistant Surgeon at the Royal Naval Hospital, Haslar, and from 1867-1871 at the Devonport Dockyard. From 1875-1878 he was Staff Surgeon in charge of the Royal Naval Hospital at Esquimalt, Vancouver Island. After his retirement in 1882 Coates practised for a time at Streatham, London. He was a member of the British Medical Association and Durham University Medical Graduates' Association, and an Hon Associate of the Order of St John of Jerusalem. He died at Dawlish, on January 13th, 1911.