Hudson Invader marine engine

The Hudson Invader was a six-cylinder marine gasoline engine that the Hudson Motor Car Company of Detroit built during the Second World War under license from Hall-Scott, the Berkeley, California engine maker whose Elbert John Hall had designed it as his last engine there. Hall-Scott had made the Invader for marine use since 1931, but once the United States entered the war in December 1941 it lacked the capacity to build it alongside the other engines the military wanted, so it arranged for Hudson to produce it in Hudson's former automobile plant. The Navy asked for 250 horsepower from the Hudson-built engine, and Hudson's version tested at 263.7 horsepower. It differed from the Hall-Scott original in being fresh-water cooled through a heat exchanger, as the Navy required, where marine engines normally used salt water. Production ran from December 1942 to September 1944 and reached 4,000 engines for the US Navy, fitted to small wooden landing craft such as the LCVP, although most LCVPs carried other engines, chiefly a Gray Marine diesel. Hudson's company article on Wikipedia says the Invader powered many of the landing craft used at Normandy on D-Day, and service literature often named it a Hall-Scott rather than a Hudson. The pages read do not state its cylinder arrangement.