Aluminium boat in steel filled former shipyard harbour

[thaisail]

The zinc anode is attached to the aluminum hull that has threads cut into the aluminum. The anode is attached with stainless steel bolts that are threaded into the aluminum hull. I am not sure what you mean about attaching a wire since the hull is aluminum and the anodes is bonded electrically to the hull via the stainless steel bolts.

[Andina Marie]

You absolutely should consider the 2.5 volt galvanic isolator plus made by Yandina. It has twice the isolation of conventional isolators. The natural voltage in the water can be as high as 0.9 volts depending on the aluminum alloy leaving only 0.3 volts of protection which can be easily overwhelmed by small AC leakage.

[YANDINA]

For an Aluminum boat, especially in an aggressive electrolysis area you should be considering the Yandina Smart Galvanic Isolator. The only isolator with 2.5 volt isolation.