Those were used on Speeditwins and Speedifours around 1947-1948. Origenly designed for the 50 horse "Storm boat motor" they had wings on the gear case to help protect the propeller. They had a couple thousand in stock preparing a big shipment for the invasion of Japan. They were suddenly surplus when President Truman dropped the A Bombs on Japan, so they used them where they could. They ran out in ’47 and the next castings were without the wings. (Most people were sawing them off anyway) In 1949 they redesigned the lower unit and added a rear water pickup in 1950. The full shift Big Twin came out in 1951. . . 😀
