I have been confident in my 1987 221 islander restoration so far. I have removed the transom, decks, and all of the flotation foam. The foam was water logged in the bow, near the gas tank, and the transom area. I pressure washed and acid etched the inside of the hull. While I was under the boat drilling out a few rivets I noticed some small blistering in the bottom paint. After scraping off the blistered paint I discovered 6 pin holes. About 1/16 to 1/8 in diameter. From the inside of the boat these pin holes were undetectable. Now I am not so confident. What caused this? Will it continue if so how do I stop it? What is the best way to make a repair? Help Please.