Lead keel plugs

[landonshaw]

I have a lead keel that is held on by 10 ss rods. These rods are 3/4 in in. dia. by 10.5 in. long threaded at both ends. A ss nut is on top and one embedded in the keel. To get to the bolt in the keel, originally the bore a 4 in. dia. hole clear through, placed a ss nut, then melted iron to encapsulate the nut. The rod screws into this from above.
The 4 in. hole that goes through the keel was left up filled by maybe 1/4 to 1/2 in. This was then filled to be flush with the outer surface of the lead keel.
My issue is that in a couple of these plugs the filler has let water in, no danger to the keel, and rust is coming out. I want to dig these few out, cove the iron with ozone, (spelling) then fill the cavity.
What should I use to fill the space between the iron and edge of the keel. I have been thinking of using the west systems 2 part epoxy with filler.
Thanks