Catalina sells lag bolts for this purpose. They are about 1/2" x 1 foot long and stainless steel. I had not noticed that the keel had gotten loose or anything but the old bolts sure looked scarry. I was told by Catalina to put the new lag bolts in between the old bolts where possible and leave the old bolts in. It is not a fun job and you need to pre drill way down into the lead of the keel with different size xtra long drill bits or you will never get the lag bolts all the way down. There is another way to do this which involves boring holes down through the keel then placing a threaded shaft into the hole then drilling through the keel and that shaft then pinning the shaft into the keel and you esentially have new keel bolts. I opted for the lag bolts just because it seemed a lot simpler. Have fun and carry a BIG cheater bar.