A motor yacht’s nice, big diesel engines are wonderful if you’re in a hurry, but they’re thirsty, not very green, and not the best of neighbors as they roar away when leaving harbor at first light. A quieter, cleaner alternative for the luxury boating market made its world première last week at the Dusseldorf Boat Show in the form of Seaway Yacht’s Greenline 48 Hybrid motor yacht.

Using hybrid electric technology combined with solar panels and a new hull design offering greater efficiency, Seaway sees the 48 Hybrid as the flagship of the company’s Greenline range and a bridge between its Greenline and transoceanic OceanClass lines.

The basic technology behind the Greenline 48 Hybrid was first introduced on the Greenline 33, but the builders say that the latest model boasts a next-generation hybrid system, a new interior design and a hydraulic transom platform that can be operated by remote control.

At first glance, the Greenline 48 doesn't look much different to any other luxury motor yachts, though a bit more sporty with a nicely rakish line to the forward glass surfaces. It’s bit tubby and sits high as such boats do, but then, they are intended more as vacation homes and entertainment venues than something designed for fighting the Roaring Forties. And it does have a very nice flybridge with a large solar panel on the front that gives a hint as to its hybrid nature.

With an overall length of 14.99 m (49.1 ft), a beam of 4.8 m (15.7 ft) and a draught of 1 m (3.2 ft), the Greenline 48 has a salón that seats eight, an electrically-operated sliding roof, three cabins, six beds, and three bathrooms complete with showers. Displacement is 13,200 kg (29,000 lb) and it carries 1,500 L (396 gal) of fuel to feed its diesel engines.

According to Seaway, the fuel consumption on the Greenline 48 is less per nautical mile than a comparable displacement hull thanks to what it calls the yacht's Protected Superdisplacement Hull Design. This is claimed to produce a very low-drag hull shape derived from sailboat hull lines that has as little as one quarter the drag of a semi-displacement, twin-engine planing boat. This makes it more stable, creating less wake, and reducing running costs.

But the centerpiece of the Greenline 48 is its hybrid powerplant. Seaway calls it a "fully electronically managed and maintenance-free system," which consists of two five-cylinder 110 bhp (81 kW) Volvo Penta D3-110 diesel engines as standard, (though three larger engines up 375 bhp (280 kW) are available), two 60-V electric/motor/generators (eM/G) putting out 14 kW, a 46 kWh lithium-ion battery array, and the 1.4 kW roof solar array made of six standard photovoltaic solar panels with forced air cooling.

The hybrid system works in one of four modes that are controlled with a single switch. In shore power mode, the system is hooked into a 230 or 120 V AC shore power supply, which charges the batteries while an inverter puts out 3 kW to run galley appliances, televisions, computers, and other gear, much as would be the case on a more conventional motor yacht. Instead of their 12 V equivalents, Greenline points out that the yacht is designed to power a full sized fridge, electric oven, television, air conditioning and other devices both underway and while docked.

In the electric drive mode, power is supplied by the batteries and the solar array for silently going in and out of harbor, and to save on fuel costs. Propulsion comes from the eM/Gs, which consume 7 kW each in the electric drive mode and generate 5 kW of electrical power when driven by the diesel engine. This puts out enough power to drive the Greenline 48 at up to 6 knots (11 km/h, 6.9 mph), while a cruising speed of 4 knots (7.4 km/h, 4.6 mph) can be maintained for a range of 20 miles (32 km) under battery power. According to Seaway, the solar array can propel the craft at 3.5 knots (6.5 km/h, 4 mph) without draining the batteries, so long as there's sufficient sunlight.

In diesel drive mode, a hydraulic VW clutch hooks the diesel engines directly to drive shafts and the eM/Gs. This both propels the craft and recharges the batteries. In this mode, the Greenline 48 can reach a top speed of 23 knots (42.5 km/h, 26.5 mph) and cruise at 7 knots (13 km/h, 8 mph) for a range of 1,000 nm (1,852 km).

Finally, there’s anchor charge mode, which operates as it says on the tin. At anchor, the solar array and engines take over charging the batteries and powering the electrics. Seaway says that in a full day of sunlight the solar array can charge the batteries up to 80 percent capacity. If the charge falls below a preset level, the engines kick in automatically to run the eM/Gs

Seaway claims this system will burn only as much fuel over a full boating season as a sailboat of comparable size or up to four times less fuel than a similar twin-engine boat while producing less noise and fewer emissions. In addition, there’s a GreenPad app that wirelessly collects data from a monitoring box in the engine rooms, so the owner can keep tabs on performance.

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