Method of replacement inner valve without leaving signs of repair outside. Patch hidden under rub strake. Heat gun used to activate glue. Glue is PVC glue for inflatable boats. Roller or spoon can be used as a tool.
There is an easier and I think better way. Remove valve by cutting 3 small cut in a triangle fashion at hole(these are probably only about 1/4". remove inner broken part of valve and replace. Install round patch over hole(about 2" in diameter bigger than hole. Recut/drill hole with a tight fit for the male half. This patch will serve to strengthen an area that is susceptable to developing leaks anyway and the valve being tightened will help if you haven't done a good job bonding. Don't make that big slice in your boat! That slice if you've gotta do it that way(but don't) only needs to be a1/4 an inch greater in diameter than the outside part(male) of the valve.
