Saildrive Zinc Usage pics - appropriate or excessive in 8.5 mos?

[ArgleBargle]

Just hauled my new-to-me Hanse 370e w Yanmar 3YM30 saildrive out for bottom paint etc. I have never had a boat with saildrive before - the engine zincs on my old (raw water cooled) shaft drive yanmar 2GM hardly seemed to get used up at all over a year (same marina as now).

Saildrive zinc was new 8.5 months ago when purchased (changed at survey haul out). old zinc had some loss (cant entirley remember how much) & saildrive paint didnt look pristine (saildrive leg was fine, though) - saildrive leg was also cleaned to bare metal, barrier/bonding coat and painted with saildrive/aluminum compatible antifouing paint at my request/surveyor's advice to be safe/certain when i bought the boat. Now zinc looks like attached pics. The saildrive leg itself looks fine.

The zinc was a bit more used up than I would have predicted. The water here is cold but there is a fair amount of flow with tidal currents. Using the methods described by Casey in "sailboat electrics etc" have checked my marina and boat for stray currents (none) and I have a (tested and functioning) galvanic isolator and use an extra zinc hung off the side and electrically bonded to the DC ground.

My question is, is this about the amount of saildrive zinc usage one would expect over 8 months or does it seem excessive? interested in opinions/experience of other saildrive owners out there.

thanks muchly in advance

[ArgleBargle]

PS - lighter discolouration on prop is marine growth not erosion/pitting and the things that look like gouges in the pics for some reason are not gouges in actuality. the prop is fine.

[celenoglu]

Although this loss can be considered high, it is acceptable depending on the area the boat is kept. I have seen similiar losses in zinc on different boats in Turkey. Water temperature does not play an important role for galvanic currents. Electrical connection to land is important but keeping the boat unearthed or using galvanic isolators should help.

[sailingdog]

That doesn't sound particularly high to me... one of my friends replaces the zinc on his sail drive every six months or so... and his boat is on a mooring without any electrical issues.