RE: kadey krogen 42 fuel and water tank construction material?
I have a copy of a 1982 construction drawing for the Krogen Manatee. The fuel tank is specified as 304 SS. The water tank material is not specified. I haven't verified my tank material yet.
You may find variation for Krogens even within the same design. My understanding (which could be way off) is at least some of the boats were built by independent contractors "licensed" by a major Taiwanese boatyard.