Sacrificial anodes: what they are and when to change them

Sacrificial anodes 'get eaten' on your behalf: they corrode so that the expensive metal parts of your engine and drive don't. They are cheap; what they protect is not.

When to change them

Check them every season and change them once they have lost 50% of their mass. If they wear out very quickly, there may be an abnormal galvanic current in the marina.

Zinc, aluminium or magnesium

• Zinc: salt water.
• Aluminium: salt and brackish water, longer lasting.
• Magnesium: fresh water.

Use the right material for your water or they won't protect properly.