Yamaha Harmo – Deafening silence

We tried out the Japanese company’s new outboard on a Capoforte 240SQi, which was specially designed to be electrically powered

by Barche – photo by Andrea Muscatello

“You can hear the mussels thinking”. That was a Venetian taxi driver’s blunt opinion. We were in the island of Murano, on a foggy winter’s day. A strange, silent engine was running in the lagoon on the transom of a small boat, which itself had rather strange lines. A group of journalists and photographers were following it. When we stopped at the quay the taxi driver was next to me, waiting for clients. His is poetic praise of the silence of Yamaha’s new Harmo. And taxi drivers are notoriously sceptical by nature. I take it as the engine passing with flying colours, as getting noticed for being quiet isn’t something that happens every day.

Harmo is decidedly something that is unusual amongst the power systems that have up to now been focused on the yachting world. Let’s start from the most obvious aspect of its uniqueness: it is an outboard but in its own way. It is indeed not the traditional combination of engine-gearcase-propeller which turn together to give thrust and direction.

CAPOFORTE SQ240i
CANTIERI ASCHENEZ
Design Christian Grande
LOA 7.38m
Maximum beam 2.46m
Weight during the test 1,640 kg
Batteries max 4x200A 48V LiFePO4

Range
8 hours at 5 knots
Acceleration
From 0 to 4 knots
 in 6s
From 0 to 6 knots in 12s

The engine is fitted to the transom on an aluminium mini bracket, and at first glance, it looks as if it could be an inboard-outboard device, but actually, the only holes that you have to make are those for the tubes that come from the batteries and instruments/controls. But everything raises electrically to get up out of the water, just like a traditional outboard.

«THE RELAXED AND SOCIABLE FEEL ON THE DECK IS ENHANCED BY A VERSATILE LAYOUT, IN WHICH A LARGE FOLDING TABLE CAN LEAVE SPACE FOR AN EXTRA CUSHION. IN THAT CONFIGURATION, THE ENTIRE BOW SECTION BECOMES A LARGE, FULL-BEAM SUN PAD».
CHRISTIAN GRANDE

But the most interesting aspect, and something not yet seen on boats of this size, is the technology used in the engine. So-called RIM Drive Technology has the propeller encased inside an aluminium ring, within which is hidden the engine, that is made up of an outside part where there are coils, reels, and an interior in which spinning magnets are connected to the four propellers. That means the power is not provided by the rotation of a traditional central axis. RIM technology is normally used on large ships, for pod propulsion and for bow or stern thrusters, clearly on a much larger scale. Harmo has 3.7 kW of power, a static thrust of 102 kgf, around what a traditional nine horsepower outboard produces, and weighs 51 kg. The ducted propeller turns 70 degrees in each direction if you use the joystick and 40 with steering wheels and throttle. As to range and charging speed, everything of course depends on the device installed on board and that is available on the quay.

On the Capoforte SQ240ì that we tried out there were two 48 Volt, 200A lithium/iron/phosphate Life PO4 batteries, that produce eight hours range at five knots. That means having a day of freedom in what is the ideal use for this pairing of boat and engine: inland waters, protected areas, or day rentals. And Venice is the perfect place for that. When at the helm I was struck by just how quiet it is, even more so than a traditional electric outboard, given that the engine is completely submerged (… so you can hear the mussels thinking) and then there is the manoeuvrability. The large rotational angle and the use of the joystick make any kind of movement incredibly easy. The unusual installation in the stern, furthermore, is a lot less bulky than an outboard, both visually and physically: getting around on the side swimming platforms is very easy.

HARMO RIM-DRIVE YAMAHA
Outlet mechanical power 3.7 kW
Static thrust 102 kgf
Weight 55 kg
Steering angle (max) 70°

As well as the Harmo, the Capoforte SQ240i can also fit the Molabo ISCAD V50, a straight-shaft onboard electric engine that produces 50 kW, which we haven’t yet been able to try out. What they have in common is of course the boat, which was made with the infusion technique used by the Aschenez Yard and designed specifically for electric use, as explained by its designer, Christian Grande: «The lines don’t have to express speed, but they do have to be harmonious, linked to a use that is relaxed, and relaxing». The most distinctive part of the design is the wide and imposing bow, which feels almost sculpted. It is a bow that increases the amount of room available.x

(Yamaha Harmo – Deafening silence – Barchemagazine.com – May 2023)