None of my thru hulls are sitting in salt water. As the parts of the seacock are in contact there is no current flowing through the water to them. If you have the older coned seacocks then you don't have dissimilar metals and even if they're from different pours of the metal I sincerely doubt there would be enough material change in even 100 lifetimes to weaken the part. There is a zinc on my prop shaft and one actually on the prop. When I've checked with a VOM on the fittings and the water and the dc in the boat there is NO current flowing. Thus; to me, I am electrically neutral. Now if a near by boat became charged and I didn't have a zinc then maybe I could have an issue. But since I have a zinc it will disappear faster then anything else and also show me that there is an issue near by. Also, should I have a lightening strike I most like will not have my thru hulls blown out. Yeah, I know that the charge can arc but that will be the highest potential way for the charge to exit the boat, by arcing, and thus the lightening will end up taking any of the less restrictive ways off the boat.

Also, although, anecdotal evidence is not the best, it seems to me from my last boat to this one and from watching those around me, that a bonded boat has more issues then an unbonded boat.

Ciao,