On board there is an adequate grounding dispersion system fitted with a porous plate which constitutes the “means” of grounding the generator PE conductor, to which all the grounds of the alternating current systems are connected as well as all the negatives of the direct current systems.
In case of yacht out of water, use protection for shore dispersion immediately restoring the contact of SHORE GROUND CONNECTION in engine room.
If the yacht is out of the water and connected to the quayside power supply, check the presence of the shore-side system in the power supply system.
Periodically check the status of sacrificial anodes and porous plate: replace if the reduction for corrosion is more than 50% of their original mass.
If their wearing is particularly quick, the on board electric system could be leaking. Have the electric system checked by experienced personnel.