The Sail-Gen shares the same operating principal as the DuoGen’s water mode, which is well proven over hundreds of thousands of sea miles. The Sail-Gen has the same geometry as the DuoGen and also utilises the same alternator, water impeller and drive train.

The Sail-Gen comprises a rigid welded aluminium frame with carbon fibre drive shaft and cast alloy impeller. It is compact in size and both reliable and efficient in operation. At typical passage speeds (5 – 6 knots) the Sail-Gen is capable of matching power consumption, freeing the owner from engine runs to charge batteries.

● The Sail-Gen is direct-drive, i.e. 1:1 ratio impeller to alternator. There is no gearbox to wear and add friction.

● The Sail-Gen’s alternator is not submerged, and is therefore less liable to failure through water ingress.

● The Sail-Gen’s running depth is controlled by a ‘hydro foil’ or ‘dive plane’. This means that the water impeller flies through the wave action at a constant depth and is not directly affected by the pitching movement of the yacht, as occurs with the ‘outboard leg’ type generator.

● The impeller running depth can be optimised by a simple adjustment of the dive plane angle.

● The dive plane prevents the water impeller from surfacing in all but the most extreme situations.

● The Sail-Gen dive plane is active, and moves to a positive angle as tension is applied to the recovery lanyard. This makes recovery simple and easy, regardless of boat speed.

● An impact wire can be fitted to move the dive plane positive in the event of a collision with floating debris. This allows the Sail-Gen to ride over the obstructions, minimising any damage.

● The Sail-Gen is built using high quality, corrosion-resistant materials, including cast aluminium impellers, carbon fibre driveshaft and a welded aluminium frame. The aluminium is hard anodised, followed by a polyester powder coat.

● The slow speed, permanent magnet alternator is robust, highly efficient and well proven. Featuring stainless steel shaft and bearings, powerful ferrite magnets and heavy copper windings, this unit is capable of sustained outputs in excess of 500 watts.

● The Sail-Gen is supplied complete with an alternator yoke and ‘c’ bracket. Together, these form the gimballed mount for the Sail-Gen and allow the unit to pivot both vertically and horizontally when deployed.

● The ‘c’ bracket should be attached to the yacht within 500mm of the centre line, and with height options of either 392mm or 532mm above the static water line. The ‘c’ bracket can be through-bolted to the transom. In some cases additional brackets may be required to facilitate the installation.

● In its ‘parked’ position when not in use, the Sail-Gen is held in a vertical position by a frame clip supplied with and integral to the mount hardware.

● The Sail-Gen is supplied in either 12 or 24 volt variants. A standard 280mm diameter impeller is available for yachts with passage speeds up to 9 knots. A high-speed 240mm diameter impeller is recommended for boats capable of speeds up to 15 knots.

● To prevent battery damage through overcharging, we recommend that a charge regulator forms part of the installation. This should be a ‘dump’ type regulator rated at a minimum of 40 amps at 12 volts.

● Drag and the resulting speed loss from water generators are often over-stated. Drag from the Sail-Gen is less than 15 kg at 6 knots, and typical boat speed losses at that speed are in the order of a tenth of a knot or less.

● The Sail-Gen weighs 16.7 kg excluding mounting.

Performance & Expectations

Reference to the charge current on a dedicated ammeter or battery monitor, in conjunction with a reading of boat speed from the ship’s log, should produce figures which correspond to the published power performance data.

If the charge current appears low for the boat speed, consider the following checks before deciding there is a fault:

● When measuring performance, the state of charge of the batteries should be taken into account. A discharged battery accepts charge current more readily than a charged one.

When evaluating Sail-Gen performance, ensure that the batteries are discharged by 30 – 40%. Alternatively, switch on multiple electrical appliances in order to reduce the battery terminal voltage.sail-gen-graph

*Note that where a charge regulator is fitted, it will act to prevent battery damage through overcharging. Surplus power diverted by the regulator to the dump resistors will not be seen by a battery monitor. A dedicated inline ammeter may also show a reduced reading when the regulator is active and the dump resistors are connected. This is because the electrical load provided by the dump resistors retards the alternator, lowering the Sail-Gen’s efficiency.

● Where low outputs are evident, first suspect loose or corroded connections. Check and re-make these connections as necessary. Also, check the cabling for broken insulation or other damage.

● Ensure that the batteries are in good condition. A defective cell within a battery will greatly reduce overall charging efficiency.

*All performance figures are indicative. Actual outputs may vary. E&OE.


When installing the Sail-Gen, due care should be exercised at all times. The Sail-Gen weighs 17.6kg and is awkward in shape with the weight concentrated at one end. It is sensible to approach installation in a methodical manner and to enlist some help when attaching or removing the machine from the transom.

If possible, install the Sail-Gen when the yacht is ashore. If this not practicable, installing in a marina with the yacht secured stern to a pontoon is a good alternative. The pontoon provides a safe and convenient working platform.

A dinghy can be lashed across the transom in order to provide additional security, if work has to be done at anchor.

To read more please view our Sail-Gen Manual by clicking here


Mechanical Issues

If the Sail-Gen water impeller continually surfaces and will not ‘re-bury’ check the dive plane adjustment, Also check that the dive plane actuating rod moves freely and returns fully under the pressure of its spring.

Typical operating dive plane angles are between 6-12 degree positive (i.e. leading edge of dive plane lower.) This means the angle between the vertical frame member which carries the water impeller, and the face of the dive plane should be in the range of 96-102 degrees when there is no tension on the recovery lanyard.

If the water impeller continues to surface, check that the alternator pivot point is the specified distance above the static water line, and that the installation is within 500mm of the yachts centre line.  Finally suspect turbulent water flow from a rudder or skeg, and re-locate the unit so it operates in clearer water.

Always ensure the ‘C’ bracket/ yoke lock screw has been released prior to deployment and ensure Sail-Gen is free to pivot laterally.

● If power output is low check for weed or debris fouling the water impeller. Also check for undue friction when the impeller is rotated. If the rotation is stiff or hard spots are present suspect bent or damaged drive pins. Also check for axial play at the impeller. There should be 1-2mm of free movement of the impeller along the axle. If this is not present suspect fishing line or similar wound around the impeller shaft at the thrust bearing.

Electrical Issues

● If there is no power output evident first suspect poor or broken connections or blown fuses. To test the alternator disconnect at the end of Sail-Gen’s output lead. Then connect a multi-meter set to the 0- 20 VDC range connected between the positive and negative cable. Spinning the drive shaft by hand should produce 3-5 volts on a 12 volt machine and 6-10 volts on the 24 volt variant. If you can produce voltages of this order it indicates that the Sail-Gen is OK and the fault lies elsewhere.

● Next check i.e. the charge regulator for a possible fault. The easiest way to do this is to connect Sail-Gen directly to the battery by passing the regulator. If the charging current now flows check the regulator manual and regulator trouble shooting guide (Available on Eclectic Website,
If no charging current is shown on the ships battery monitor, ensure Sail-Gen is connected to the non-battery side of the shunt which drives the monitor. Refer to body of this manual for further information.

Also the 6TB12 and 24 type regulators have an integral charge splitting function, i.e. can charge two battery banks simultaneously. If only one battery bank is monitored any ‘missing’ charge may be passing to the other battery bank.

Where the water impeller rotates very slowly but no mechanical friction is evident there may be a short circuit in the Sail-Gen’s output cables. To check disconnect Sail-Gen at the end of its output cable and see if the rotation frees up. Note – Short circuiting the output of Sail-Gen produces on electromagnetic braking effect.


Sail-gen Manual

Sail-gen Routine Maintenance

The Sail-Gen is built from high quality and corrosion-resistant materials. The unit is designed to require minimal maintenance, but a little attention will pay dividends in terms of appearance and performance. The alternator requires no routine maintenance and is hermetically sealed.

The alternator is fitted with rubber-shielded, stainless steel bearings which are protected by a twin lip, radial shaft seal. A dry-running spherical, self-aligning bearing is fitted at the top of the tower. Elsewhere, dry-running bearing bushes are used. The water impeller unit utilises a specially designed transmission which presents the impeller perpendicular to the water flow. The transmission element is robust and maintenance free.

It is lubricated by a combination of synthetic oil held within the bearing material itself and water. When dry following immersion in seawater, the unit may feel stiff. This stiffness is usually due to dried salt deposits and the drive should free up when the unit is returned to the water.

The Sail-Gen’s water impeller rotates about 5 million times for every thousand miles sailed, and like all mechanical devices, the water transmission is prone to wear.

Eclectic Energy recommends that the transmission elements are replaced every 8 – 10,000 nautical miles, after approximately 40 – 50 million revolutions, in order to maintain optimum performance. This is a straightforward procedure that can be undertaken by the owner.

A full range of spare parts are available for the Sail-Gen in our Shop section under Sail-Gen Parts. All spare parts are supplied with fitting instructions.