I wouldn't get worried so much regarding the fin on The underside, just seal it up so it doesn't leak. Ironically I welded up a lower unit just two times in the past. Dude strike a rock and punched a hole while in the front of his unit, dug the https://miloqjugp.shotblogs.com/the-ultimate-guide-to-outboard-lower-unit-repair-45742568