Your anodes protect your boat against natural galvanic or, even, accidental electrolytic corrosion*. They must be adjusted precisely to give the correct protecting potential: too high, your hull or equipments will corrode, too low, immersed coatings can suffer from blistering (peeling paint and antifouling). The damages can be significant, needing costly repairs**. There is a simple test to check, afloat, that your anodes (wether new or worn) are operating correctly and to detect the possible presence of harmful stray currents...

* Electrolysis in boating world. ** Not covered by your insurance.