Wire wheeled the joint and it was 95% just cracked paint along the caulking between the hull/keel. The other 5% was some fairing that was used to just finish up the connection for smoothness.
Went to West Marine and they wanted to sell me some 2 part flexible expoy for $40. Seemed too much for what it was. In the end just masked it offt and put down a layer of Life Caulk. It's good in water and paintable for the bottom paint
later. Not excatly smooth, but enough for me (maybe I will made it smoother if I run out of real things to work on). Now I have a nice black rubber 1" line around the keel.
If I remember I'll report how it worked out when the boat gets hauled end of the year.