The transformer isolates your boat from the shore power so that galvanic currents do not occur in your 230V system. It is an old misconception that there is no risk of galvanic corrosion in a fiberglass boat.
Isolation transformer in 2000 Watt or 3600 Watt with built-in soft starter, step up and step down (120VAC /230VAC). Phase, neutral and ground are all isolated.
