I wouldn't fret much with regard to the fin on The underside, just seal it up so it will not leak. Ironically I welded up a lower unit just two days back. Guy hit a rock and punched a hole during the front of his unit, dug the chunks and https://eduardofbgmp.thelateblog.com/32258750/not-known-details-about-repair-boat-lower-unit-fin