Yea, there are plenty of those out there. I wouldn’t bother trying to save it. Either that is a factory flaw, or somebody smacked a log with it. First one I’ve ever seen like that. Good info to have.
I believe the big twin manual will swap up to 1967 or 68 then they made changes in the water tubes and impeller housing. The later ones up to 1970 will also work, but you have to swap out watertubes and impeller housing. I bought a 69 gear case and and put it on my RDSL-21B
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