I think a must is to install a galvanic isolator
Before I installed one I hung a zinc "guppy" connected to the engine
block and immersed in the sea. With that, the zincs were near the end of their life at haul out
every 20 months. With the isolator, the zincs still have a lot of life after as long as 40 months.
I also am an advocate for installing a oil
header tank for the sail drive oil
. I have had them for over 15 years.