Several different companies offered marine conversions for Ford Model A engines, but the one in the original post is a marine engine conversion made by Lehman Marine Engineering Company out of Newark, NJ.....thus the "L M" initials on the gearbox cover emblem.
Here is a photo from the 1935 Lehman Marine catalog and parts list showing that marine engine, along with its original specifications, dimensions, etc.
That engine was available as a complete engine and gearbox (three variations) or as a kit (four variations). Lehman Marine also offered a similar complete marine engine or a kit, for the Ford Model B engines and the Ford V8 engines, with various add ons, modifications and accessories available for each.
Brad in Maryland