Thanks for the link and answer. My other boat
is left kept, so never was an issue. This is all new to me.
My '95 new to me cruisert has twin Alpha drives that were corroded pretty bad and I am replacing both the drives and the transom assemblies with new, so wanting the best protection. My new transom units have the sacrificial anodes though. I will replace those with the exterior Mercathode unit and internal controller during the reinstall.