"Rod McInnis" wrote in message
...

"Matt/Meribeth Pedersen" wrote in message
ink.net...

Especially if a wooden boat is overprotected, the more noble
fitting creates sodium hydroxide, which eats away the lignin in
the wood.

I don't understand what you mean by "overprotected".

Overprotected means having too much zinc in comparison to the more
noble metal, i.e. having five zincs on your prop shaft when only
one will do the trick. When it comes to protection, the "some is
good, more is better" theory doesn't work.

ABYC recommends, for wooden boats, a potential of -550 to
-600 mV, in reference to a silver/silver chloride cell.

I think I know what you are saying about the more noble fittings, which
would be the various through hull fittings.I have seen the wood
surrounding
the fittings become deteriorated and spongy to the extent that the plank
had
to be replaced.

Lots of woodenboat owners don't bond their through hulls together
and certainly don't put a lot of zincs on the boat.

Are you saying that they don't, but should? Or that they don't to avoid
the
effects you are talking about?

They don't to avoid the effects.