The principle is simple: using the speed of the boat to turn an immersed propeller and produce electricity.

An innovation: Watt&Sea has engineered a hydrogenerator with excellent output, performance, and reliability.

In 2015 we became a dealer for Watt&Sea Hydrogenerators for Canada and the USA – and our customers elsewhere in the world. A green product that is very much in line with our high standard of quality and engineering, the Watt&Sea is, like the Hydrovane, of huge value to the offshore cruiser.

I can’t wait to mount one on our Hydrovane!

– Will Curry

10 Reasons to choose Watt&Sea

  1. High electric output – 24 Amps at 7.5 knots of boat speed
  2. Negligible drag because of leg and blade shape
  3. A source of free green power
  4. No need to run the engine to charge: saving in fuel consumption
  5. Completely quiet
  6. Lightweight
  7. Easy to install, especially with the Hydrovane bracket
  8. Maintenance-free
  9. Has a sleek design and look… just like the Hydrovane!
  10. Designed and manufactured by top racers and engineers in France

Mount the Watt&Sea on your Hydrovane

Install your Watt&Sea in the perfect position – attached onto the Hydrovane shaft.

This unique installation, exclusive to Hydrovane owners, means no extra holes in the transom and allows easy use and removal of the Watt&Sea.

See the Galleries section for photos.

Part NameGBP £EURO €USD $CAD $
Hydrovane's Watt&Sea Mounting Bracket (pair)474593593742

The Brackets could also be used for other purposes – like an outboard engine mount if you ever needed emergency propulsion. We are in the process of designing an specialized engine mount to fit easily and quickly onto the Watt&Sea brackets.

Watt&Sea Cruising Series

Contact Will for a complete quote.

The Cruising series hydrogenerator is a simplified variation of the racing version – less expensive as it is not manufactured of carbon fiber.

  • Available in two outputs: 300 or 600 Watts
  • Available with two leg lengths: 610 or 970 mm *same price
  • Includes one 240 mm propeller (the 200mm and 280mm propellers are options)
  • Uses “brushless” technology
  • The 12-24 Vlt regulator has an advanced electronic architecture
  • It is 2kg lighter than the RACING series, which makes lifting and removal even easier
  • It has been redesigned with optimized hydrodynamics
  • The generator housing has enhanced corrosion resistance
  • Start-up speed: 2 knots

Which model, leg, and propeller size is best for me?

Please email Will with your boat type, a photo of the transom, average cruising speed, and shipping location. He can provide further information, answer any questions, and send a complete quote.

Can I use the device while I run my boat main engine?

The system in not designed to replace the alternator of your engine. It can nevertheless be used while running your main engine although the output may be lower because of engine propeller turbulence.

What should I do when I’m in port?

You may either leave the device on the transom in the lifted position, or remove and store it away if you have the space. If not lifted, it is necessary to have lines that prevent the cradle and blade from backing against the transom.

Is there a risk of damage to the batteries?

No. The regulator monitors battery voltage levels.

What happens when my batteries are fully charged?

The electronic regulator monitors battery levels and when fully charged the propeller switches to “freewheel” which diminishes the drag.

What type of batteries can it charge?

The system is compatible with any type of battery: lead (acid or gel), lithium… If you have special batteries Watt&Sea can set the output for you before shipping.

What if I hit something?

The lifting system has a release in case of impact. However, the risk of direct impact on the device is quite minimal given its position on the transom, behind the keel or centerboard, and rudder.

What speed loss is to be expected?

Watt&Sea doesn’t have any specific data on the effective drag of the device, or about the speed loss it generates. All immersion and lifting trials at constant speed have not shown any substantial difference on the speedometer. Testimonials back this up.

Can I replace the propeller?

Yes, replacing the propeller is simple and only requires an allen wrench and an extractor screw.

How should I maintain the device?

Wash down the outside with fresh water from time to time.  The device does not require any specific maintenance.

What is the anti-corrosion treatment?

The aluminum parts are anodized, and coated with paint. They are also electrically insulated from the other metallic parts to prevent electrolytic corrosion.

How reliable is the system?

The Watt&Sea has been designed with the latest technology. All metal parts are made either in specially treated aluminum or in 316 stainless steel.

The generator housing is sealed with hi-tech ceramic-carbon gaskets. These gaskets have a lifetime of several thousands of hours and will painlessly support a circumnavigation.

The housing is filled with a lubricating oil and slightly pressured to prevent any water seepage.

In addition, the alternator is immersed in a resin that encapsulates electrical conductors. Should any dampness occur, the electric parts would not be damaged.

Overall, the system is impeccably designed and built – and is therefore highly reliable.

What power output can I expect?

The power generated increases exponentially as boat speed increases. At 5 knots, the output power is about 120W (or about 10A on a 12V battery) with the 280mm propeller. At 8 knots, the system produces 4 times more power, i.e. 480W (about 40A on a 12V battery raw). The output may differ depending on sea conditions.

To reload a 200 Ah 12V battery bank to 50% of its capacity, on average, 10 hours at 5 knots or 3 hours at 8 knots would be necessary.