J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Bilge space under mast step?

No - that is solid and a structural area where the two hull halves are joined together. There is nothing but fiberglass and epoxy there. Not a good idea to be drilling into that structural area. I'd check with a pro and have it looked at. You may have weakened that area and to properly fix, it may need to be ground back with new glass and epoxy layed up to properly spread the load. Just filling the hole with epoxy will have very little strength.

Think of the pressure that is excerpted there with the rig adjusted and wind on. You now have created a stress point right below a very high load area. The potential exists for that load to start cracking an area that you just weakened.