Silicone Warning -- Being a used boat dealer I see many fixit projects from the DPO (Dreaded Previous Owner). Many people have used silicone as an adhesive, or smear it around leaks. After a while the silicone releases from whatever surface it was applied on and the boat is back to having the original leak that the silicone was supposed to fix. It is my experience that silicone is only good as a gasketing material that is between 2 materials that are in compression, such as a sealant between an inspection port and the plywood underneath. If you are looking for a material that you can smear around on top of a hole and have some hope of fixing a leak, consider using "marine goop" which has great adhesive properties, yet stays very rubbery and can be removed with just mechanical force.