Through Hull seacocks below the waterline.
may help you. The short version is to test them. If you are really willing to pull all of them for replacement, then pull all of them for inspection
. My boat is 1988 and I believe the thru-hulls are original. But one (or all) could have been replaced at any time, gotten dirty, etc.
Replacing Thru-Hulls and Seacocks Photo Gallery by Compass Marine at pbase.com
is another site I have used as a reference. It has good pictures and I am following the advice to replace the existing backing plates
. Either cut from some boatyard scrap or as one person recommended, taping wax paper over the hole and making one myself with a custom fit.
At the same time I am putting a protection ring around the seacock. I am still working on what exactly to use. The intent is three fold: 1- protect the sea cock from someone accidentally tossing something onto it and damaging it. 2- Keeping it clear of anything in case I need to get to it. 3 - ensuring I have a plug
that will fit in case the worst happens.
Other seacock bookmarks I have:
Seacock Removal and Replacement
Surveying Fiberglass Sailboats: A ... - Google Books