I’ll go with ’48 as my father traded in a ’48 Sportsman back in ’63 for a new Johnson CD 5.5 and the serial number on it was 52777, a bit higher than yours. A few years back I aquired and restored another ’48 Sportsman and the serial number on it is about 15 digits different from the one on the ’48 which got traded in. I figure OMC must have filled a boxcar full of motors built on the same shift and then shipped them out to the coast here.
