A well-known UK manufacturer of marine equipment for over 80 years, Ailsa Craig Motor Co. Ltd was named after a landmark offshore rock on the western Scottish coastline near to Ayr, although they were based in England. Ailsa Craig held the Royal Warrant as suppliers of Marine Motors to King George V. The company was among the first in the UK to build hot-bulb diesel engines, although they dropped them fairly quickly with the advent of direct injection and the start of WW1, when they were required to produce goods for the war effort.
They continued with smaller engines up to the 1960's, but eventually closed.
The engine shown is a 10hp unit with bore and stroke of 7" X 9", running at 400 rpm. Ailsa Craig made their own injection equipment for the early engines, and although fairly simple and low pressure by modern standards, they gained the company a reputation for reliability and economy amongst their customers. Later engines used first the Acro pre-combustion chamber, then the Ricardo Whirlpool chamber. The company made engines up to six cylinders in the 1940's and 50's, with eight and twelve cylinder engines listed in trade publications of the 1940's.
The gearbox shown in the picture includes the clutch and reversing gear, all operated by the single lever.