Marine air conditioning for a 50 ft boat
Chilled water becomes the sensible architecture around here, especially with four zones. Below that a locker fills with compressors.
50 ft Boat Cooling Requirements by Climate
A 50 ft hull (15.2 m) is roughly four cabins of accommodation. The sizer works from the volume that has to be cooled and the seawater the unit has to reject its heat into, so the same boat asks for a different machine depending on where it lives.
| Where it lives | Cooling needed | Same in kW |
|---|---|---|
| Tropics — Cairns, Darwin, the Whitsundays | 29,000 BTU | 8.5 kW |
| Subtropics — Brisbane, the Gold Coast, Perth | 24,500 BTU | 7.2 kW |
| Temperate — Sydney, Adelaide, Hobart | 20,500 BTU | 6.0 kW |
8,500 BTU separates the same boat in Darwin from the same boat in Hobart — about the output of a whole small unit. This is why a figure quoted without a climate is not a figure. Run your own case on the sizing calculator; these rows are that calculator with the length fixed.
Air Conditioning System Layout for a 50 ft Boat
Chilled water. A chiller feeding fan coils, each cabin on its own thermostat.
Supplied and fitted, including the seawater side and the electrical work, ex GST. The equipment alone is $16k–$24k of that; the rest is parts and 60–110 hours of yard time.
About $4.48 for a night at anchor or alongside, at 2.34 kW and the duty cycle a closed-up boat actually sees. Roughly the cost of leaving a light on, which surprises most people.
That leaves 0.3 A of a 10 A marina lead and 5.3 A of a 15 A one — for the kettle, the battery charger and everything else aboard.
Prices are ranges computed from the cost model, not quotes. The same boat lands at either end depending on access, how far the ducting runs and what the yard charges.
Marine Air Conditioner Options for a 50 ft Boat
Webasto BlueCool C27, Dometic Chilled water, Mabru SC12DC — the Chilled water units on this site, closest rated output first. On a boat this size the choice between them is usually decided by where the box will physically fit, not by the specification.
Cabin Layout and Installation Checks Before Ordering
Every figure above is arithmetic, and arithmetic does not know where your locker is. Tell us the boat and the home port and we will tell you whether the numbers survive contact with your layout — including, sometimes, that a wind scoop would fix it for a hundred dollars.