Is this ‘crossover day boat’ the finest to emerge from the modern Sealine stable? After taking a test drive, Alex Smith suspects the Sealine S390 might be exactly that...
There’s a distinct trend going on in the day boating world – a trend toward spacious, versatile open boats that are also able to provide enough accommodation for longer family cruises.
We’ve seen it in stylish cockpit-centric powerboats like Jeanneau’s DB line and in De Antonio’s high-volume outboard-powered party platforms. And those same basic crossover underpinnings are equally evident in Bill Dixon’s latest Sealine design.
For a start, there’s the beam. At 12ft 8in, the Sealine S390 is certainly quite wide for a boat of this length and the cockpit is carefully set up to embrace pretty much all of that. It uses a single access point on the starboard side to maximise the breadth of the aft bench.
It also uses quite narrow bulwarks to maximise internal space and the hardtop is supported by a pair of stanchions that reach right out over the gunwales. The fact that there are strong steel bars inside these moulded uprights means they can afford to be very narrow too – and that’s in spite of the fact that the hardtop itself is quite a complex piece of kit.
In addition to speakers and spotlights, it provides a big sliding sunroof above the helm, plus an even larger retractable soft top that projects aft, above the bench, between a pair of rigid roof extensions.
Unlike most sunshades, you can run with this out at top speed – and although (like most of the equipment on this boat) it’s an optional extra, it’s a fine feature and something a boat like the Jeanneau DB/37 would do very well to emulate.
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Alfresco party zones
While it’s by no means an overtly ingenious space, there is a bit of modest convertibility in the big aft cockpit. The backrest for the aft bench, for instance, folds flat above the swim platform and the table drops into the space with a cushioned infill to create a big sunbed.
In the future, this table will be increased in scale with a forward leaf to take better advantage of the port bench and it will also come with a set of branded directors’ chairs to improve sociability as part of the standard package.
Ahead of that, the two-part galley, built into the aft edge of the helm seats, is also quite practical. It provides plenty of space for fridges and ice makers without impeding the broad central companionway.
But the way the cockpit space is used here is not quite as hardworking as you might expect of a serious day boating platform. There’s no integrated furniture in the centre of the deck for passengers who want to seek extra shelter under way.
There are no fridges in seat bases or reversible backrests to face forward or aft. And while the starboard shore power socket takes it closer to the wiring looms, it makes little sense to position an exposed cable on the same side as your sole point of access.
It seems to us that the standard swim platform is a bit stubby too, so for day boating versatility, the extended platform would be well worth the money, adding a valuable couple of feet so you can open out the cockpit sunbed without obstructing your watersports zone.
Having said all of that, the basic scale of the cockpit space remains very impressive and access to the side decks is equally good. The steps dovetail beautifully with the hardtop design to ensure that you don’t bang your head while making your way fore and aft.
And the bow space itself is also a surprise because, in addition to the traditional island sunbed, you also get a neat little forepeak recess, where the deck level drops away. That enables you to use the low-level backrests at the forward edge of the sunpad to sit down and face ahead toward the cushion-topped anchor locker.
It’s certainly very intimate up here. In fact, it looks almost comedically tight for four. But it’s a charming little chill-out zone and an uncommonly secure and comfy place for the select few to get away from the main cockpit party.
Sleeping for five
As you tend to expect on boats of this size and type, the lower deck space is closely linked to the furniture management of the cockpit and foredeck.
In this case, that means you get a transverse mid cabin with excellent space beneath the elevated port co-pilot seats and surprisingly accommodating headroom beneath the helm’s raised deck. There’s a pair of transverse singles in here plus a third bed running fore and aft along the port side.
It’s spacious enough to sit up in bed and there’s excellent natural light and generous views, thanks to long, deep windows on both sides of the hull.
Further forward, in the central lounge, the L-shaped dinette uses a drop-down table and cushioned infill to create either an occasional berth or a lounge area so you can put your feet up and look across to the TV built into the starboard bulkhead.
And that starboard side exhibits more clever work from Bill Dixon. It comprises a heads and shower compartment forward and an L-shaped galley aft. The loo sits in the shower compartment to help free up extra space for the galley – and the galley itself is neatly arranged, with a two-ring gas hob, plus an oven and a large fridge with freezer compartment.
It also uses a simple sliding partition (rather than blinds or a curtain) to block out the light and as a rigid wipe-clean panel, it’s easier to maintain and much less likely to go wrong. To further reduce cost and complication, the various deck hatches are also handle-free.
Sealine has instead elected to supply a compact handheld rubber plunger to lift each panel out of the deck. That makes plenty of sense and it certainly looks that bit tidier but just make sure you buy spares, because losing your only plunger would prove a proper aggravation.
And so we come at last to the owner’s cabin. Perched up in the V of the bow, it is, by any measure, a bright and attractive place to be. In addition to the overhead skylights, there’s a huge window in the leading edge of the foredeck’s island sunbed, plus long raked hull windows on either side.
The relatively beam-forward design and steep hull sides enable the bed to encompass a really generous footprint. It only tapers a little bit at the very head end, right up above your shoulders, and the vertical space is also fantastic, enabling you to sit up in bed with more than a foot to spare above your head.
Of course, if you want an extra cabin or an extra loo, you need to look toward the Sealine C390. But with a proper heads compartment, a dedicated galley, a serviceable lounge and comfortable sleeping space for five people, the weekending credentials of this day boat are absolutely first-rate.
Sporting in name…
As a member of the Sport line, the Sealine S390 has to perform and it does exactly that. Put the hammers down and there’s a satisfying surge that takes you through the transition to plane with zero fuss or delay. In the turn, the heel is quick but prodigious, driving you down into your seat rather than sliding you sideways on it.
This boat also feels extremely settled and compliant, enabling you to tweak the direction and attitude at wheel and throttle with really commendable finesse. You’re able to push on far harder than you might have anticipated but in spite of all that driving fun, it also delivers a very satisfying combination of openness and refinement too.
Thanks to the one-piece screen, wide open sides and big overhead sunroof, all-round visibility is superb – and yet the four upper helm seats enjoy all the protection you could want.
Even at the 34-knot top end, your hair remains completely unruffled and, while the bolster position puts the screen rim directly in your eyeline, the seating position is nigh on perfect. And in any case, if you do decide you want to stand up under way, it’s easy to drop the foot brace, pop your head out of the sunroof and operate that way instead.
Cruising efficiency looks perfectly manageable too. With a pair of 5.5-litre, six-cylinder D6 380s, we’re seeing a fuel flow of around 4 litres per nautical mile at everything from 20 to 30 knots, but there are other engine options.
You could opt for the 3.7-litre, four-cylinder D4 320s instead, and that would certainly free up a little extra space in the engine bay, but do you really want to drop the top end from 34 to 27 knots? Do you really want to work the engines harder for a decent cruising speed? And do you really want to give away some of that watersports-friendly poke?
We would suggest that you ought to forget about the smaller engine option. With its top-rated D6s, this test boat is great fun in terms of its handling, sustainable in terms of its efficiency and commendable in terms of its urgency.
It could easily do the job for watersports as well as day cruising and while it isn’t seismically rapid, it delivers a helming experience that is at once as comfy and as engaging as anything in this market.
As we make our way back up the Hamble toward TBS Marine’s base at Mercury Yacht Harbour, we just need to mention the hull colour.
While it won’t be for everyone, the test boat’s Aquamarine Violet finish has a pleasant habit of morphing in relation to your perspective. And because the hull features lots of faceted angles, bulges and recesses, even standing still creates a range of hues from deep-sea blue to glittering turquoise.
It’s such a pleasing addition to this boat’s feel-good vibe, it’s an option we might even be tempted to take. In line with most Sealine boats, the S390 needs a lot of optional ‘extras’ to bring the standard package up to the kind of spec you would want.
The test boat, for instance, costs just over £600,000 (around £125,000 more than the base price) and includes plenty of non-standard necessities like tables and a TV, as well as cosmetic upgrades to the deck and upholstery.
For proper day boating versatility, you would also need to compensate for the cockpit’s relative simplicity with the addition of some freestanding furniture, plus the electric sunshade over the aft deck and the extended (or even hydraulic) swim platform.
But the fact remains that the Sealine S390 is a beautifully judged boat. It treads pretty much the perfect line between day boating and cruising, between openness and protection, between style and practicality, between volume and driving dynamics.
And whether you’re into day boat parties, a sporting drive, cruising as a couple or full-on family fun, that makes this modern crossover dayboat one of the best you can buy.
First published in the August 2023 issue of MBY.
Sealine S390 specifications
LOA: 39ft 4in (11.99m)
Beam: 12ft 8in (3.85m)
Draft: 3ft 11in (1.19m)
Fuel capacity: 900 litres
Engines: Twin Volvo Penta D4 320s or D6 380 sterndrives
Test engines: Twin Volvo Penta 5.5-litre, six-cylinder D6 380 sterndrives
Top speed on test: 34.3 knots
Fuel consumption: 78lph @ 20 knots
Cruising range: 185nm @ 20 knots
Noise: 86.3 d(B)A @ 20 knots
RCD category: B for 10 / C for 14
Starting price: £479,681 (inc. VAT)
Price as tested: £607,901 (inc. VAT)