the "bonding" at the rudder that connects the zincs with all pieces of metal that have contact with salt water is to protect these metals (avoiding galvanic problems). It is not to be used as "electrical ground" or earth connection. Therefore you should not connect any ground/earth connection from any electrical device to this grounding point.
in addition to that, imho, there is no need for connecting the ground of your solar panels, they will work fine if not grounded :-)
fair winds, herbert
KALI MERA, SN120, back in Mazatlan NCB