All mine ARE grounded... but I wonder, is isolation a better approach? Could the thru hulls be better off of they were isolated via a Marlon valve for instance? (Does Marlon thread onto Bronze?)

For about a year my whole boat was isolated... at least from ground... I didn't have a connection to dockside power.

Now of course different metals on the boat itself can cause ionic currents, but I believe you need some sort of complete circuit... and if seawater cannot complete the circuit through a valve, and there is no ground connection, would the bronze thru hulls be better off?

Larry brings up a good point... that the engine shaft can be the other connection... but if it too is isolated?

Can an "open circuit" protect your boat?