I have had a standard Perko scupper (flapper) on my boat for years. It finally rotted away and I replaced it. I have tried (3) different brands including Perko and have been unable to find one that will seal and not let the boat fill up with water. It sits about 8-9" under the water line and is fed internally from a self bailing box in the rear of the boat. ANy help would be greatly appreciated. DOes anyone know if the "Ball" type scuppers work below the water line or are they for water line transom use only..?