When Broads based I had Aluminium on Kiki as a compromise, particularly moored at Goodchilds.
When we moved Kiki to permanent salt it was surprising how they disappeared and were quickly replace by Zinc.
I would thoroughly recommend a Galvanic Isolator for what they cost, much cheaper than new stern gear.
Before and after here viewtopic.php?f=37&t=2948&p=137655&hilit=galvanic#p137655
viewtopic.php?f=37&t=2948&p=125847&hilit=galvanic#p125847