Dux is one of the many Swedish engine makers who made a wide range of engines for the fishing boat market, and subsequently developed other markets using modified versions of the boat engines. In the UK, an installation of twin engines in a 40ft motor yaught was carried out in 1913.
Single cylinder engine sizes ranged from 4hp at 800rpm (4" X 5" bore and stroke) to 32hp at 300rpm (11" X 15" Bore and stroke) with twin cylinder versions of most of these being available. Air start was available for engines of 25hp and upwards.
A couple of scanned pictures from an old 1909 text book on hot bulb engines.
More information to be posted here.