Can I use a domestic split system air conditioner on a boat?
No. A domestic unit rejects heat into the air and needs airflow a boat cannot give it, and it is not built for salt. It will lose capacity and corrode quickly.
Can I use a domestic split system air conditioner on a boat — Explanation
The price difference makes this tempting, and it comes up constantly. It does not work, and the failure is not obvious on day one.
A domestic system dumps its heat into the air through a condenser designed to sit outside in open air. On a boat there is nowhere with that airflow — a lazarette or a cockpit locker recirculates its own hot air, so the unit progressively heats its own supply and loses capacity exactly when you need it. The coil, the casing and the electrical side are all built for suburban air rather than salt, so corrosion is fast, and no manufacturer will honour a warranty on a vessel.
Marine units are water-cooled precisely to solve this. They reject heat into the sea, which is why they can live in a sealed locker with no ventilation at all and still work at full capacity on the hottest day of the year.
Equipment Specifications and Installation Checks
This answer is a practical starting point for Australian boat owners, not a vessel-specific instruction. Confirm the unit manual, electrical supply, seawater layout and current product specifications before spending money or changing the installation. Refrigerant and fixed 240 V work require appropriately licensed people.
Use the official resources for licences, standards and manufacturer documents. If the answer does not fit your boat, ask Gabriel. Advice can be incomplete, out of date or wrong; see the disclaimer.