I have rambled all over the place on this subject. Let me say one last word on the importance of checking galvanic isolators if you have one on your boat.

About five years ago David Rifkin and Jim Shafer did some research on electrical shock drowning (ESD). ABYC received a grant through the Coast Guard on ESD. ABYC then hired Dave and Jim to do a study on ESD.

Jim and Dave traveled all over the USA setting up their experiment, mostly at fresh water marinas but I think they also did this research in brackish and salt water marinas.

Dave is a Corrosion Certification Instructor and Electrical Instructor for ABYC. He is a Certified Marine Surveyor also. This is only a few of his credentials.

What he has found in his experience is that 5% of all galvanic isolators that he tested had presented an open ground and the boat operators were not aware of this.

Once you have an open ground, you now have one of two faults needed to create an electrical accident. If another fault were to occur, then you have the potential for lethal harm.

One of those harms can mean that your under water metals are now conducting lethal current into the water (most important in fresh water) causing nearby swimmers hearts to stop or causing paralysis of the swimmers muscles and then drown if they don't have a life jacket on. The other way that two faults can cause harm is if someone in the boat touches or comes in contact with the boats grounding system resulting in a lethal amount of current.

So if you have a galvanic isolator, test it according to the manufactures recommendations even if you have an indicator and test it regularly. Or even better install a fail safe one but still tests this one too regularly.

My 2003 Catalina has one tucked away in the stern locker where the shore power comes in. There is no indicator on it. It takes me twisting like a pretzel to check it. I'm not sure when they stared putting those into their boats.