Had all my bronze thru hulls/sea cocks replaced with year with marelon after a total failure of the thru hull
due to corrosion
. So far they are doing well. I have had no issue with them seizing up or difficulty with operating them, but of course they are new. Older ones will need the hose taken off, then greased, then operated a few times to distribute it. A hassle sure, but so was the bronze ones letting go.... And for what they cost, I can afford to replace them every 10 years or so if need be.