Originally Posted by 79pmooney

Fresh water or salt? There's an order of magnitude difference between the two. In salt, you might well need zincs in contact at key places to save the less noble metals. I've spent a lot of time around boats and salt water but mine were always lightweight racing sailboats and the metals were marine aluminums and passive stainless steels. I wish my dad was still around to help you. He had an ocean going sailboat with lots of metal and kept it (in very good shape) for 30 years.