This years service and upgrading-corroded throughhull (trawlerfans)

Noticing an increasing brown staining from the throughhull regulating the blackwatertank in aft cabin I was a bit concerned.
Being just below the waterline now on the hard we took the valve out. First I thought the leak was in the threaded joint between valve and pipe, but when tightening the joint (after sealing) the pipe of the throughhull cracked into pieces !
Looking closer the pipe (which seems to be stainless) was heavily corroded and cracked just in the middle.

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