I'd be replacing everything (thru hulls, valves, nipples and hoses) based on those photos. I've just been removing my old Jabsco
toilet and knocked the 3/4" ballvalve which snapped off below on the thru hull
stem. A small fountain of water sprouted, before I could hammer in a plug
. That looked a lot less corroded than those in the pictures!
Anyway, I've decided to replace my bronze ? brass ? (who can really tell) thruhulls and ballvalves with Forespar Marelon fittings. Why? No more corrosion worries. The spec's say same strength. Maybe just need to take care with the handles and keep up the lubrication. They were not cheap
, but I think it's good insurance