Education... photographic identification of electrolysis.
Fit the SeaBis System - its the most economic way for you to protect your installation.
Clutch oil pressure sender.
The original marine - two wire isolated sender had been replaced by a land one wire sender. A proper marine sender was fitted for less than Au$100. That was the only defect onboard. Now a $250,000 commercial fishing vessel is free of electrolysis.
Note:
Electrolysis current commonly follows a weld. The reason is the weld has lower electrical resistance than the sheet metal.