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Cathodic protection control of metal or wood/GRP hulls propulsion systems is to your boat what anti-theft alarm is to your house. Regularly performed, it warns you before electrolysis damages become too important, and so, costly. So, don't wait to discover a sinister, during annual scrub-off for example, to deal with it: corrosion dammages are never covered by insurance companies. If this sail-drive is replaced without control, problems might occur indefinitely...