Most modern Maxi Yachts (along with many other makes of yacht) are fitted with Volvo Penta engines with sail-drives. It is essential to understand how the anodes protect the saildrive and the prop, and to test/inspect at appropriate times…
Galvanic protection to the saildrive installation is implemented using a ring anode bolted to the sail-drive leg. This anode protects the leg and sometimes the propeller from corrosion. If this anode doesn’t work properly or replaced when worn, your saildrive may corrode – horribly expensive! Later models of saildrive anode can be replaced without removing the propeller.
The two and three bladed folding propellers currently use anodes bolted to the propeller for galvanic protection. Older propellers (and some non-Volvo-Penta folding props) do not have these anodes and rely on the leg anode for protection.The Volvo-Penta folding propeller fitted with anodes is electrically isolated from the propeller shaft, the propeller without anodes is not.
The anodes are intended to reduce the risk of dezincification, which makes the prop very fragile: you can tell if dezincification has occurred by the reddish colour and a dull metallic sound instead of a clean “ring” when tapped.The Leg anode only protects the leg as the leg is electrically isolated from the engine. Owners should ensure that additional electrical work does not electrically connect the leg to the engine or electrical ground. My opinion is that additional hull anodes connected to the engine ground will not have any effect on leg or propeller corrosion.
Related topics: 1100 propeller size, Rope cutters, Propellers and Anodes,
Mick