Report on our Experience with the Watt & Sea 300 Cruising

This blog is for anyone interested in the Hydrogenerator Watt & Sea.

To increase our power supply during sailing, we had a hydrogenerator installed: Watt & Sea 300 Cruising with long shaft (970mm), large 280mm propeller.

Our ship is a Hallberg Rassy 43 MK III built in 2013.

The Watt & Sea performs well in theory. In practice, it is difficult to handle. The installation was sloppy. It was was carried out in September 2017 in Gibraltar by a German W&S representative. Because we were a „yacht in transit“ there, we did not have to pay VAT. Overall, the installation including travel expenses of the rep to Gibraltar cost us 5,200 euros. The installation took about 5 hours. The charge controller was fastened under the bed right next to the AGM batteries. The W&S was installed at the lowest possible point of the transom with the original W&S universal bracket on the port side.

So far so good. We were looking forward to our first test sail from Gibraltar to Tenerife ….. 5-6 days on the Atlantic Ocean. But….

Problems due to incorrect installation:

Right after the initial start-up, after crossing the Strait of Gibraltar, it became apparent that W&S was not performing. It made extremely loud noises and strong vibrations that could be heard throughout the ship. It sounded like somebody was machine sanding the stern – absolutely annoying! We let the W&S run all day, hoping it would eventually show some performance. In the evening and for the night noise and vibration were no longer bearable. We took it out of the water and saw that the line that lowers the generator was almost worn out.

Our agent from Germany assumed that the software of the charge controller was not programmed for our AGM batteries. After Saphir was hauled out for the winter , we removed the charge controller and we took it to Germany to be reprogrammed. It would have been appropriate to have done this before installation. Another point: the Velcro strip used to fasten the controller to our bed could not withstand the motion. It fell down in heavy waves. We fixed that by adding an aluminum bracket later.

In December 2017, Saphir went back into the water and we reinstalled the newly programmed charge controller. We also replaced the lines for lowering and lifting the W&S with stronger ones.

On the way from Tenerife to the Cape Verde Islands we had the same problems as from Gibraltar – noise and vibration. The W&S LEDs indicated that it has a connection problem. It was not functioning again and we had no W&S electric power on this route whatsoever. In Cape Verde, we asked an electrician to find the connection problem. W&S was ready to pay for one hour of service. The electrician quickly found a loose connection, repaired it and we were hoping that the W&S was now fit for the big Atlantic crossing to Barbados.

Not even close! For the 2,000 nautical miles across the Atlantic to Barbados we had exactly the same problems again – no power from the W&S. End of January an electrician in St. Lucia checked the connections and saw that the contacts in the plug did not match the ones in the socket. How could that happen! All the parts were installed as supplied by W&S. The repairs were paid for by the German agent since it was obvious that the installation had been performed very poorly. It was also clear that better performance checks would have been necessary – measuring the charge through the wiring over all 3 phases rather than relying on the LED display of the controller would have revealed the false connections in alle 3 (!) phases.

By end of January 2018, five months after the first installation, the W&S functioned for the first time! But unfortunately only for a short time …after 300 nautical miles in the Caribbean with typical winds up to 20 kn and moderate waves, the bracket of the W&S bent under the pressure and even the „low friction ring“ needed for lowering the unit into the water wore out.

This is the status today, seven months after the installation. We will have the fixture completely refurbished in St. Lucia to correct these flaws and to improve the handling of the W&S, which has proven to be very difficult under normal conditions of use. W&S asked us to send the bent part to France at our expense for examination and offered to send a new one at their expense. The whole thing probably takes 4-6 weeks to complete. Therefore, and because we have no confidence in the bracket, we refused the proposal.

By the way: We met other sailors with a W&S. Only one of them had not experienced problems. He had never used it before.

Now to the handling of the W&S:

1) With the W&S you can not shift to reverse while it is in the water, that would damage it.

2) You should not use it at all when running the engine because then the alternator already takes over the load and the W&S makes noise and vibrations.

3) You cannot lower the W&S while sailing, because the force of the current will prevent it from lowering to the right position. So you always have to stop to lower it!

4) Also, it is impossible to remove Sargassum from the shaft without stopping. At present, the Atlantic and Caribbean are full of Sargassum though (an alga with a behavior like creepers), and it wraps itself around the shaft and obstructs the propeller. It is absolutely annoying to free the propeller and shaft again and again. Sometimes you’re lucky and a bigger wave washes the stuff away. However, our W&S is not suited for the conditions we have encountered.


There are two lines for lifting and lowering which are led through a curry clamp. When both are in it at the same time – and that’s usually the case – nothing works. The system blocks itself. So you have to – even with 7 kn speed and good waves – bend down far (you lie with the belly on the deck) and pull the nonused line from the curry clamp.



To hoist the unit from the water, you must use a pulley which has been mounted somewhere on the deck to lift the 40 kg maximum load. The line quickly becomes an additional pitfall.



It is also annoying that the hoisting line always detaches itself from the track and hangs sideways. You lose your leverage and can not hoist the unit. Again, you have to lie on the deck, strech your arms 80cm down the transom again and guide the (red) line back into the track.




To make the whole system safer I installed two extra curry clamps and a small cleat directly above the W&S. I was concerned that the one W&S clamp would not be enough to reliably absorb the water pressure of up to 300 kg over a long period of time.



When raised, the W&S swings left and right with each wave – another weak point. We therefore pulled an elastic line to the rear cleat to hold the W&S in one position. This solution was the official recommendation of the German agent. It works, but it looks really cheap.




Another point: to deinstall the W&S you have to raise the longitudinal axis. A ring is conveniently attached to the top. Unfortunately, it is so close to the rest of the installation that you almost cannot get it out, especially since you have to hold on to the W&S at the same time, which would otherwise fall into the water.




Last but not least: our W&S is mounted much too high. For our ship the so-called universal bracket won’t work.

It was still installed, and we trusted the agent, not knowing the propellor should really be about 30 cm under water. Now, with big waves and especially when heeling to starboard, the W&S is out of the water most of the time – where it is useless.




One more word about the performance of W&S:

We are satisfied with that. Our ship has a hull speed of just under 9 knots. In reality (trade winds up to 20 knots) we usually sail with 6-8 knots. Then the W&S brings 10-12 amps. This is almost sufficient to compensate for the power consumption of our two plotters, freezer, refrigerator, autopilot, AIS, VHF, Navtex and tablets and we can arrive with almost full batteries at the anchorage. Only 3-5 amps need be drawn from the batteries. There is almost no noise and vibration and no diminished speed through the water for a cruiser.

Would we install another W&S again?

A very conditional ‚yes‘: Only if the mounting bracket is stronger and adapted to our ship. Also, handling would have to be much better. Obstructions such as Sargassum should free themselves, the W&S should be able to stay in the water with the engine running, and it should not swing when out of the water. We have the impression that the focus of the W&S developers was primarily on electrical performance and too little attention was paid to practical operation. There is still room for improvement!

2 Gedanken zu “Report on our Experience with the Watt & Sea 300 Cruising

  1. Thank you, that was very interesting. We thought this could have been a good solution for power, but now it puts us off. Seems like Watt & Sea needs to do some more improvements!

  2. Hi and thanks for all the photos and time you invested into this report. As i understood, the big issue has been the wrong installation from someone who you paid a lot of money. I think, this should be highlighted in the header or at least beginning. Most people do not read the full article and are leaving before they know the full story. Anyway, thanks for sharing your experience and wishing you fair winds and following seas.

Kommentar verfassen

Trage deine Daten unten ein oder klicke ein Icon um dich einzuloggen:

Du kommentierst mit Deinem Abmelden /  Ändern )

Google Foto

Du kommentierst mit Deinem Google-Konto. Abmelden /  Ändern )


Du kommentierst mit Deinem Twitter-Konto. Abmelden /  Ändern )


Du kommentierst mit Deinem Facebook-Konto. Abmelden /  Ändern )

Verbinde mit %s