Watermakers for boats 33 to 40 feet.
This is the most common cruising size on the Australian east coast, and the band where the decision genuinely matters. There is usually enough space and enough bank for a real installed system, but almost never a generator — so the watermaker has to live inside the solar budget rather than beside a diesel.
The electrical reality at 33–40 ft. Typically a 12 V house bank, solar, occasionally 24 V. Solar and the alternator, with no generator to fall back on. Watt-hours per litre is the number that decides whether the system runs at anchor or only under way.
What matters at 33–40 ft
The solar budget is the real constraint
After the fridge, a typical boat this size has a few hundred watt-hours a day genuinely spare. Multiply that spare figure by nothing — just compare it against each system's daily energy for your litres, and the shortlist writes itself.
There is room, but not much of it
A modular system that mounts in three pieces will fit places a single frame will not. On boats this size that flexibility is often worth more than the difference in specification.
Short daily runs beat long weekly ones
Membranes prefer regular use, and a daily run in the middle of the day comes straight off the panels rather than out of the bank. Size so the day's water takes an hour or two, not four.
Check the intake with the boat heeled
On a monohull sailing hard, an intake on the high side can suck air. It is a plumbing decision made at install time and expensive to revisit.
Shortlist for 33–40 ft boats
The 10 best matches of 23 that suit a boat this size, ordered by energy per litre. Run time and energy are for 66 litres a day.
| System | Power | Output L/hr | Draw W | Wh per litre | Price |
|---|---|---|---|---|---|
| Zen 30 Schenker | 12/24V DC | 30 | 110 | 3.7 | $6,300 |
| Zen 100 Schenker | 12/24/48V DC or AC | 100 | 400 | 4.0 | $9,600 |
| Ventura 150 Deluxe Spectra | 12/24V DC | 24 | 108 | 4.5 | $6,000 |
| Ventura 150 Connect Spectra | 12/24V DC | 24 | 108 | 4.5 | $7,400 |
| Newport 400C Spectra | 12/24/48V DC | 64 | 288 | 4.5 | $14,500 |
| Zen 50 Schenker | 12/24V DC | 50 | 240 | 4.8 | $7,800 |
| D100 DUO Dessalatorreported | 12/24V DC | 100 | 700 | 7.0 | on request |
| D60 Freedom Dessalatorreported | 12/24V DC | 60 | 550 | 9.2 | on request |
| D60 DUO Dessalatorreported | 12/24V DC | 60 | 550 | 9.2 | on request |
| Portable 48VDC 140L Rainman | 48V DC | 100–154 | 1,250 | 9.8 | $6,240 |
Common questions
- What size watermaker for a 38 foot yacht?
- Three aboard at a normal cruising 22 litres each is 66 litres a day. Look for something that makes that in one to two hours, then check what those hours cost in watt-hours against your real solar surplus — that second test is what narrows the list.
- Do I need a generator for a watermaker on a 40 foot boat?
- Not if you choose an energy-recovery DC system. Those are the ones that fit inside a cruising solar budget. A conventional pump at this size generally means running the engine, which is fine if the engine runs daily anyway.
Not your size?
Before you shortlist
Length is a proxy, not a measurement. 66 litres a day is 3 aboard at 22 litres each — a planning figure for boats of this size, not a claim about yours. Two people cruising frugally on a 45-footer use less than a family of four on a 38. The shortlist is filtered to systems whose power source and output suit a boat this size and ordered by energy per litre. Watt-hours per litre is rated draw divided by rated output. Methodology.