Was only the inference that one must have zincs on ss that I was referring to - proper selection of materials will not require that. Where poor materials or a poor combination of metals has been specified then anodes will be necessary. In some few cases vulnerable mixed metals come with the territory eg sail drives, variable props, etc and anodes will be necessary.
As I said, for the shaft and a bronze prop in a well specified boat it should not be necessary to use anodes on them unless to protect vulnerable mixed metals in a variable prop.
The common situation where anodes are fitted in association with ss is on alumnium vessels but in that case the anodes are to protect the aluminium.
Yes our boat is steel. Apart from the prop shaft (with manganese bronze, which is actually a brass, prop) and rudder
stock we have some other ss underwater welded to the hull itself - the only care needed is to treat the transition at the weld from ss to the mild steel as mild steel for a short distance over the ss due to carbon migration from the mild steel into it, but that is just a matter of extending the hull plating coating system an inch or so over the ss part.
We only have one light anode on the boat, that on one side of the fin keel
and it lasts easily 2 years and we have no galvanic or electrolytic corrosion problems whatsoever. The anode loss is probably mostly at its natural corrosion rate in seawater so it is in fact likely redundant.
I think it would be quite possible to build an alumnium boat without anodes (and I believe our own steel one would be fine without) but due to the vulnerability of aluminium is probably not a secure approach.
So it is quite possible to specify a boat, even of steel, that does not sail around with a crop of anodes connected to the other underwater metals, turning the whole boat into a zinc/bronze/ss etc, salt water
with short circuit currents flowing around it all (the anodes and the "protected" metals form short circuited batteries through their bonding conductors). One just has to know what one is doing and not believe everything one reads about corrosion in forums, because it is mostly incorrect.