Watermakers for motor yachts
If your boat has a generator that runs daily, most of the efficiency argument on this site does not apply to you — and that is worth saying plainly. You are buying litres per hour and dollars, not watt-hours.
The power reality. With a genset or shore power available, a 240 V system's kilowatt-plus draw is covered by machinery that is running anyway. That buys the highest output per dollar in the table.
What matters on motor yachts
Make water during the evening genset run
Sizing so a day's water is made inside the hours the generator already runs is the cleanest arrangement on a motor yacht.
Buy the larger membrane pack anyway
Even on a generator, more membrane area for the same pump means less run time and less wear per litre. The efficiency figure still tells you something useful.
Higher water use is normal
Motor yachts tend to have more heads, bigger showers and deck washing. Thirty-five litres a head is a realistic planning figure rather than a pessimistic one.
Consider the genset-off case
If you sometimes lie at anchor without running the generator, a DC system as a second option — or a DC-capable model — avoids starting machinery just to shower.
Shortlist for motor yachts
The 8 best matches of 19 that suit motor yachts, ordered by litres per hour. Run time and energy below are for 140 litres a day.
| System | Power | Output L/hr | Draw W | Wh per litre | Price |
|---|---|---|---|---|---|
| Frame AC 240L Torrent, auto Rainman | AC 240V | 180–264 | 2,800 | 12.6 | $15,089 |
| Frame AC 240L Torrent, manual Rainman | AC 240V | 180–264 | 2,800 | 12.6 | $12,089 |
| Performance Triple 200L · 12V feed Water Makers Australianameplate estimate | AC 240V | 200 nominal | 1,610 | 8.1 | $9,181 |
| Automatic Triple 200L · AC feed Water Makers Australianameplate estimate | AC 240V | 200 nominal | 2,280 | 11.4 | $19,250 |
| Performance Double 140L · 12V feed Water Makers Australianameplate estimate | AC 240V | 140 nominal | 1,610 | 11.5 | $7,791 |
| Portable AC 140L Rainman | AC 240V | 100–154 | 1,250 | 9.8 | $5,329 |
| Portable Petrol 140L Rainman | Petrol | 100–154 | — | petrol | $6,731 |
| Modular AC 140L Rainman | AC 240V | 100–154 | 1,250 | 9.8 | $5,460 |
Common questions
- What watermaker is best for a motor yacht?
- Usually a conventional 240 V AC system with a large membrane pack. With a generator covering the draw, these give far more output per dollar than the energy-recovery units, and the efficiency premium buys you a benefit you are not short of.
- Do I need a generator for a boat watermaker?
- For an AC system, effectively yes — they draw over a kilowatt. DC systems at 12, 24 or 48 V run off the house bank without one, which is the route sailing boats take.
- How big a watermaker for a motor yacht?
- Work from crew and habits: four people at 35 litres a head is 140 litres a day. A 140 L/hr system makes that in about an hour, which fits neatly inside a normal generator run.
Guides that go deeper
Not quite your boat?
How the shortlist is built. 140 litres a day is 4 aboard at 35 litres each — a planning figure for this kind of boat, not a measurement of yours. The list is filtered to systems whose power source suits motor yachts and ordered by litres per hour. Every figure is the manufacturer’s rated output and draw; Wh per litre is one divided by the other. Where the closest Water Makers Australia model falls outside the normal power filter, it is included as a disclosed 240 V Australian alternative. Methodology.