Most people looking at a 1991 motor yacht expect the engines to be the big question. With M/Y ‘Contentus III’, the replacement has already been done: she was fitted with two brand new John Deere diesels in 2018, and De Valk lists just 65 running hours on them since.
But the engines are only part of her appeal for me. I love her styling, from the white, high-sided hull with its blue stripe to the long rectangular windows. I love that she’s steel throughout: hull, superstructure and deck. I think she’s in great condition and ready to go. And I love how spacious she is, which is exactly why the question in the title is worth asking.
The essentials
Contentus III is a Moonen 56, built in 1991 and offered by Julian de Heer at De Valk Loosdrecht for €355,000, VAT paid. That’s roughly £300,500 or $396,800 at the European Central Bank’s reference rates for 7th October 2026.
She measures 17.80m x 4.75m, with a 1.60m draft and 2.00m of headroom. Her round-bilged steel hull has a full keel and twin rudders, and her decks are teak over steel. She has 3 cabins and 6 berths, and 2 x John Deere 4045 AFM85 diesels of 180hp each, on shafts, give her a listed maximum of 8.5 knots. Her CE category is recorded as exempt (I explain why in the premium section below).
A superyacht yard’s steel beginnings
Moonen describes itself today as a Dutch boutique superyacht builder. After doing some research, I found that its story began with LADY M, delivered in 1981, which set the yard’s reputation for long-range yachts with steel hulls and aluminium superstructures. Moonen’s own fleet history shows an impressive run of steel motor yachts through the 1980s and 1990s, and that’s where Contentus III belongs. She comes from the chapter before the superyachts, and she’s a way to own a piece of the yard’s much earlier work.
The 2018 repower
Her two 180hp John Deeres went in new in 2018. They’re freshwater-cooled through heat exchangers, with dry exhausts, and turn fixed propellers through PRM hydraulic gearboxes and Aquadrive thrust bearings. On a 1991 boat, that’s a major job already done. What 65 hours means for a buyer is one of the things I also cover in the premium section below.
Why steel, and why this hull
There’s a practical reason Dutch steel yachts have such a loyal following. Steel can be cut and welded if a repair or modification is ever needed. Her round-bilge displacement hull is designed to move through the water rather than climb onto the plane, and her listed maximum is 8.5 knots. De Valk describes her as ideal for extended stays on board, and the specification shows what that means: Naiad Multisea II stabilisers to damp roll, hydraulic bow and stern thrusters for tight marinas, and double glazing as well as foam insulation.
Life aboard
The deck saloon is the heart of her, with a dinette, a sliding door to the aft deck, and teak joinery and floors. The galley has granite worktops, a Neff electric cooker, a Siemens dishwasher and fridge, a separate Electrolux freezer and a microwave, and there’s a Candy 3.5kg washing machine.
The owner’s cabin has a double bed and is served by the main bathroom, which De Valk lists as shared. It has a decent-sized bath with a shower in the tub and a double basin, and a bath on a 17.80m motor yacht is worth pointing out, especially if your better half insists on one. The guest double has its own shower and toilet, and the third cabin has L-shaped bunks, handy for children, grandchildren or an extra pair of hands.
For year-round comfort, there’s diesel central heating (listed as a Webasto D8LC) and 16,000 BTU Frigoboat air conditioning. Her electrics are set up for living aboard, with a house bank of twelve 2V Mastervolt cells rated at 748Ah, a Mastervolt Mass Combi 24/4000-120 inverter-charger, two isolation transformers for shore power and a Fisher Panda generator with 600 hours. A dedicated hydraulic generator drives the thrusters. Up top, the flybridge has a second helm, a deck crane handles her Carib DL11 tender and its Honda outboard, and her mast lowers electrically.
Her fresh-water tank holds about 1,500 litres. West Marine’s guide to boat water systems suggests 4 to 8 US gallons (roughly 15 to 30 litres) per person per day for comfortable living with full showers and regular cooking. At that rate, assuming the whole tank is usable, a full tank lasts about 25 to 50 days for 2 people, 12 to 25 days for 4 and 8 to 17 days for 6. Run the bath often and you’ll be nearer the shorter end, but for a couple that’s still weeks between fills!
How she compares on De Valk’s books
I looked at De Valk’s other current steel listings of 17m to 18m, checked on 8 October 2026:
- The Eurotrawler 1750: €449,500 VAT paid, at De Valk Costa Blanca: 16.95m x 5.20m, built in 2005 and launched in 2006, with twin 145hp Ivecos.
- The Pacific Prestige 170: €450,000 VAT paid, at De Valk Corfu: 17.30m x 5.35m, built in 2007, with twin Volvo Penta D6-280s.
- The Vennekens Trawler 1800, €695,000 VAT paid, at De Valk Sneek: 18.00m x 5.40m, with a steel hull and deck and a composite superstructure, built in 2010, with twin 255hp Caterpillar C7s.
All three share her three-cabin, six-berth layout, and each is newer, beamier and asking more. I give my view on what that difference means in the premium section.
It’s thanks to my premium subscribers that I’m able to keep my YouTube channel and this publication going, writing about and filming boats like Contentus III. So, if you’re a premium subscriber, or you become one, a huge thank you for your support.
This article continues below, in “The Wardroom”
In the premium section, I cover:
- A year at a Dutch berth: a dated, published 18m berth tariff near Loosdrecht, with shore power and water costs, and what the figure leaves out
- What 65 hours really means: the John Deere 4045 AFM85 explained, what the repower spares an owner and the three things I’d check
- How far can she go? Why I won’t quote her range yet, and the one measurement that lets you work it out
- No CE category? What “exempt” and categories A to D mean, and what her build says about the waters she suits
- My honest assessment: who she suits, what steel asks of an owner and how her price sits against De Valk’s other steel yachts
A year at a Dutch berth
Let’s start with a local benchmark for the cost that comes round every year, whether you cruise or not.
