The area next to the rudder is in need of repair but what is there? Is a fiberglass sheath covering bolts (for what?) as has been suggested? Or is an uncomplicated repair required? Tha area is all swollen and delaminated looking.
The triangle shaped bit you're wanting to repair looks like the shoe on the end of the skeg that hosts the lower bearing for your rudder. If you want to drop your rudder, you will remove this bracket and the rudder will drop down. Fairly common construction technique
Google image search for " skeg shoe rudder removal" and you'll see quite a few photos / diagrams showing this
Sorry no photos. The swollen delaminated stuff was stripped off revealing metal which was checked for corrosion (none present), and primed. Then a grp expert carefully built the part back.
I recommend talking it through with an expert or two.