Mas,
First of all which 1947 Sea King do you have? Model ending in 9011A or 9012? They are different. The 3hp leg resembles the later
model 1947 Sea King. I’ve done the conversion between the 5hp models but not the 3hp. Several components need to be changed in the
gear case for it to fit the leg(mid section). Most of the other Gale brands use the gear case similar to the 9012 model in 1947-1953.
These are other variants:
1947 Viking C2G3
1947-48 Hiawatha 25-7971 (2H3)
1947-1948 Royal 2A3
1947-1948 Sea Bee 2G3
*JUST* before I got into collecting my mother moved, and sold an old Sea Bee of that era that my father and brother had toyed with (not sure if it was a 3hp or a 5hp), so I have a fascination with those years!
I do not know about the 3hp models. I mess with the 5hp ones. The part number for the gear housing and bushing assembly is
590177. That is from my 74GG9011A print. I don’t have a print for the 3hp.
There are 3hp with the "large" 5hp gearcase and there are 3hp models with the newer "small" gearcase. No way will the small one work on a 5hp of any model. Actually, without model numbers of the specific case you are contemplating installing on your GG9012, it would not be a real good idea to say it will or will not work.