M_Boats: Transom Wood Rot

Hi All, Here’s a nice one.. was noticing some weeping of brown sludge at the transom of my M17. I removed the bottom rudder pivot bracket to find that silicon was used to bed these bolts and water has likely been seeping in for a long time. The wood in there is now essentially earth. My plan now is to drill out that block of wood/earth and replace with a new chunk of wood or just go with a pure fibreglass/epoxy or polyester resin mixture. It looks like there is a roughly 4”x 4” block embedded in the fibreglass there. Can anyone chime in and give any details of the wood that is in that area and any other advice they might have for this repair? Thank you, Jason Leckie Point Roberts, WA / Vancouver, BC 1980 M17 ‘Kuma’