Over the years the center tanks have been subject to pitting and therefore must be considered suspect. The center fuel tank was installed, deep in the keel, before the liner was in place (see photo);
Photo courtesy of www.WhitbyBrewerSailboats.com
If anyone has the names of these two guys please post them as I would like to ask how future owners were expected to replace this tank. The simple answer is that these tanks are not replaceable without major surgery, not an uncommon fact on many sailboats of this era. Some owners have cut through the hull and replaced them, but this is a pretty major job (This photo is not a Whitby).
Even if the tank appears fine at the moment I had to consider two possible scenarios;
1. The tank would leak in harbour and the bilge pump would pump the fuel overboard, with obvious unpleasant legal and environmental consequences.
2. The tank would leak on passage where I had planned on needing the fuel.
Either possibility I choose not to risk.