It would help if you told us your boat model!
My boat is a 2002 44, and has 4 external anodes. 2 on the bow thruster , a ring anode on the saildrive, and a nose anode on the Brunton’s propeller.
The ring anodes I buy from Zincsmart UK, and they will supply a machined one to fit the Ambassador rope cutter if you have one.
The prop. nose anodes I purchase from Bruntons at huge expense, as I have not been able to find an alternative cheaper source.
Hope this helps,
Michael.
