We just finished our keel bolt repair
We just finished a keel bolt repair on our 1978 30-foot Catalina. We used 8-inch lag bolts ordered from Catalina, a long drill bit (Catalina Direct), and some 1/4-inch thick stainless steel washers custom-made by a metal shop. Instead of removing the entire keel stub (wooden layer), we had some advice from Catalina for a modified procedure: using a hole-saw on your drill, drill a 1-1/2 inch hole wherever you want to put a new lag bolt. After drilling a pilot hole, drill carefully throught the upper layer of fiberglas and then through the layer of wood. Avoid drilling into or through the lower layer of fiberglas (the hull!). Clean out and dry out the hole, and fill with fiberglas. We also cleaned/scraped the bilge, and put a layer of fiberglass on the bilge bottom to cover all of the new fiberglass "plugs". Mark the plugs to make sure you can find them when the fiberglas has cured. Then drill through the fiberglas plugs and hull, into the lead keel. Install the lag bolts with washers. In our experience, you may drill into the existing keel bolts, because they are turned and run horizontally in the keel. In that case, measure the depth of the hole until the point where you hit the old keel bolt, then cut off the end of your lag bolt accordingly. We now have 5 new lag bolts installed, two of which had to be cut down to about 6 inch lengths. With this modified procedure, the lag bolts/washers are secured through a thick layer of solid fiberglas, and are not in contact with the keel stub (wood). When completely finished, we covered the lag bolt heads and washers with a further 1/8-inch layer of fiberglas.
