Re: 1957 Johnson 10 hp bucking and banging
I didn't recall OMC making any radical changes back then but in checking my parts books, apparently they did.
The 1957 10hp Johnson L/U bolted on with 5 bolts and the top driveshaft seal installed directly into the gearcase housing. The original seal part number was 41-62 and superseded up to #321788. I don't know if there was a midyear change BUT...........
The 1958 10hp Johnson which looked externally identical excepting the paint scheme, upon looking closer... the lower unit bolted up with only 4 bolts and the top driveshaft seal installed in a separate housing under the water pump which then attached to the gearcase with a gasket between the two. That top driveshaft seal is part #303345. I think I'll sit back and see what develops.