Maury shared this rare ad for an upgraded marine-purposed engine. The date on the ad indicates these motors were built starting at least in 1945, which means they were probably using surplus engines (even though fighting wouldn’t end int the Pacific Theatre for a couple months.)

I’ve assembled this approximate history based on a few sources. .Kermath began selling boat motors as early as 1913, according to this article. By 1930 they were the largest seller of boat motors in the world, based on their own advertising. Sometime in the 1940s Kermath added the jeep engine to its line of marine motors. After the war, Kermath sold Ford, Mercury, and Jeep engines for use in boats. The company folded in the late 1950s.