it doesn't need an hour of welding repair. it needs a new deck. It's swiss cheesing everywhere, and getting worse. I think salt gets trapped under the deck edges above the beams and rots it from there. Fix for future longevity is probably to seam seal inside and outside of the beams after welding on new treadplate. The centers of the spans are still fine and even have some paint left, but from the edges in for 4-6" are scale and getting some holes.
Probably no gain in resale from someone who doesn't look up from underneath and see the daylight, repaired at all or not. The top looks great and it's still solid right now and probably for a while yet, but it needs it for my continued peace of mind. Since the top does still look juuuust fine, it's going to sneak up when it really does become an issue.