I would not worry a lot 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. Dude hit a rock and punched a hole while in the front of his unit, dug https://keylargoboatseats10986.blogripley.com/32145331/the-5-second-trick-for-lower-unit-skeg-repair