Review: Seakeeper M26000 Active Gyroscopic Stabiliser

By: John Willis, Photography by: John Willis, Barry Ashenhurst & Seakeeper

Gyro boat stabilizers have been in use by the shipping industry for decades. However, small boat stabilisers are now becoming commonplace, with marine equipment like the Seakeeper stabilizer.

Hydrodynamic gyro stabilizers for boats are not new to the marine industry. There have been many versions over the last century, mainly in larger shipping applications, but the technology is now filtering through to lighter commercial and even recreational craft, meaning small boat stabilisers are now a realistic option.

The development of stabilizers for boats was perhaps hampered by efforts that mainly concentrated on external fin-style boat stabilizers. However, American company Seekeeper was founded in 2002 "for the purpose of researching, developing, and marketing motion control devices for boats under 70m" and setting its sights firmly on perfecting marine gyro stabilising technology. Their product, the Seakeeper Gyro, began manufacture in 2008 after extensive trials and now boasts sales and services offices throughout the world, including well-known transmission suppliers Twin Disc in Australia.



Seakeeper boat stabilizer

Seakeeper Gyro stabilisers have now been fitted to many Australian boats, including the well documented fitting of a unit to a new Maritimo A50 Aegean Enclosed back in 2009. Another featured heavily at the 2013 Riviera Festival of Boating onboard a Riviera 51 Enclosed Flybridge.

Worldwide, units have been fitted to well-known brands including Azimut, Sunseeker, Fairline, Princess, Ferretti, Marlow, Marquis, Carver, Ocean Alexander, Ovation, Viking, Couach, Zeelander, Terranova and Pershing as well as a range of commercial boats.



Calypso Star Charters

Port Lincoln’s (South Australia) Andrew Wright knows the importance of stability on the water. He is the primary skipper and part owner of Calypso Star Charters’ Shark Cage Diving tours which operate regular diving excursions deep into the Southern Ocean to Neptune Island in search of the great white shark.

It’s a 32nm journey each way, through the beautiful Boston Bay and passing by the many islands in between the larger Thistle Island and the mainland’s Lincoln National Park, then straight out to sea due south. These are big powerful seas with some nasty rips and cross currents and, hence, a large, high-capacity and very seaworthy passenger craft is required.

The Calypso Star II is a 19.95m Conquest fibreglass monohull with a beam of 6.2m, 1.85m draft, weighing in at 45 tonnes dry. She’s an all-weather capable vessel in current South Australian Survey 1C, powered by a 1450hp CAT C32 engine with a cruise speed of 14kts. Hence, it is a realistic two-and-a-half hour journey each way, with up to five crew, skipper, engineer, host and deckhand and a maximum of 45 passengers.

Passenger comfort, safety and enjoyment are of paramount priority in such a world-renowned tourist attraction. It is always a truly international adventure with many clients travelling from distant lands to experience the might and awe of the great whites at horrifyingly close range. The majority of passengers aren’t seafarers so the Calypso Star II must be as stable as possible to ensure happy customers and ultimate success. She must not only be stable whilst underway, but even in the lee of the Neptune Islands, as there can be quite some swell and windage buffeting the anchored boat.

Calypso Star II is clearly a solid, seaworthy and stable boat in her own right but skipper Andrew Wright was attracted to Seakeeper as he saw the advantage of added stability both underway and at rest. Fin-style stabilisers may work quite well underway but are very limited at rest. And with up to six divers in the shark cage at a time, attached to the back of the anchored hull, stability is vital.

"My main motivation in choosing Seakeeper was that it works at rest; there’s no need to upsize gensets due to its low power consumption; and there are no external fins that could potentially harm the sharks. I read extensively on the internet and everything pointed towards Seakeeper as being the best." said Andrew.

Andrew’s search quickly led him to Australian Seakeeper agents, Twin Disc, who recommended the Seakeeper M26000 Active Gyroscopic Stabiliser.



Seakeeper M26000 Gyroscopic Stabiliser

Gyro stabilisers for boats are a little hard to describe verbally but here goes. Imagine a large enclosed disc, spinning at high speeds (in this case up to 5000rpm). The disc is enclosed in a capsule on a hydraulically controlled pivoting cradle. The disc has a moveable axis point that will adjust g-forces in a computer-controlled stabilising direction.

Our clever mates at Wikipedia describe the action like this: "The ship gyroscopic stabiliser typically operates by constraining the gyroscope’s roll axis and allowing it to ‘precess’ either in the pitch or the yaw axes. Allowing it to precess as the ship rolls, causes its spinning rotor to generate a counteracting roll stabilising moment to that generated by the waves on the ship’s hull. Its ability to effectively do this is dependent on a range of factors that include its size, weight and angular momentum. It is also affected by the roll period of the ship." (Note: ‘precession’ is a change in the orientation of the rotational axis of a rotating body – like moving the Earth’s North and South poles to change the balance.

In the case of the Calypso Star II, forward predictions were that the installation of the Seakeeper M26000 Active Gyroscopic Stabiliser would achieve up to 60-80 per cent roll reduction, using the 1338kg unit. In fact, the official sea-trial report concluded a massive 87 per cent reduction in roll of the vessel’s natural period with a significant wave height of 1-3m in 15-18kt winds over a 10-minute-on and 10-minute-off test period.



Stable deck on Calypso charter

In our practical experience, the improvement in ride and stability is very noticeable, even to the boatful of novices we had on board for our test day. While the unit may take up to 75 minutes to achieve its maximum rotation speed, the unit is operational and stabilising the vessel after only 30 minutes (at 60 per cent of its rated speed).

The benefit of the Seakeeper was immediately evident to me, as I had experience with the vessel in previous ventures. We hit the rough stuff coming out of Boston Bay, hitting wind against tide and swell as we rounded Cape Donnington. It was more than obvious from the flybridge that, whilst we had some forward/reverse rock at the centreline length while we tackled short sharp slop that Andrew fittingly described as "6ft high and 6ft between ‘em," we had virtually no roll, with the gyro stabilising the side-to-side motion beautifully.

We busted into a 20-25kt south-easter all the way to the Neptunes, with a very comfortable ride considering the conditions. There was some seasickness on board – however, I personally believe many of the passengers were more prone to ‘excited motion sickness’ due to the thought of the real life sea monsters they were about to meet face to face.

"Yes, some people still get seasick, but we have certainly noticed a large reduction. Also, of the people that do feel crook, pretty much all of them come good at the island and dive, whereas pre-gyro, many would be crook all day," said Andrew.

Throughout our day of shark sighting we manoeuvred in tight turns in the swell, circling the multitude of schools, crossing our own wake and pitching into the swell. All the while, I was conscious of the added stability generated from the gyro. If the passengers knew the difference in riding comfort, then they too would have been more than thankful.

At the end of the long day’s travel, we did some further testing as we ran back up the calm waters of Boston Bay. Andrew demonstrated the effectiveness of the Seakeeper M26000 Active Gyroscopic Stabiliser by pulling up suddenly and steering briskly to port to allow the slowing momentum to coincide with meeting the large wake on the aft beam. We tried the manoeuvre first with the gyro engaged and I was amazed to find the hull completely stable with virtually no aftermath roll as she settled.

We got underway and Andrew repeated the manoeuvre with the Seakeeper M26000 Active Gyroscopic Stabiliser turned off. I watched a large percentage of the passengers physically turn green as the big hull rocked to and fro for an extended period.



Calypso charter shark diver

This final test certainly confirmed the ability of the Seakeeper M26000 Active Gyroscopic Stabiliser and proved in practical human terms the most impressive results of the official trial. Andrew’s only hesitation in choosing the Seakeeper Gyro was what effect the noise and electromagnetic interference produced by the spinning gyro would have on the sharks.

"I was assured by Twin Disc and Seakeeper that their units had been installed in many a gameboat with no effect," he said.

"I’m happy to report that we have noticed no change in shark or fish behaviour since fitting the gyro."

Seakeeper produces a range of units installed on more than 140 brands, with vessels ranging in size from 30ft upwards. Seakeeper now has over 2400 units in operation.

Seakeeper is distributed in Australia by Twin Disc (Pacific) who provide full installation and service back-up across Australia.



Seakeeper Gyro Stabiliser

Rated speed


Anti-rolling torque at rated rpm

56,000 Nm

Spool-up time to rated RPM

75 minutes at 20°C ambient

Spool-up time to stabilisation

30 minutes (60% rated rpm)



AC motor


DC control




AC Motor

1000-3000W(sea state dependent)

DC Control


AC Input Voltage

208-230 VAC (+/- 10%), 50/60 Hz Single Phase

DC Input Voltage

24V DC @ 10Amps

Sea water supply to heat exchanger

15.1 lt/min (4 gal/min)

Maximum ambient air temperature




Gyro envelope dimensions

1.28 length x 1.42 width x 0.94 height (metres)




55G Druces Road, Manukau

Phone 09 262 3241





3/10 South Quay Boulevard, Port Lincoln SA, 5606

Phone +61 8 8682 3939





See the full version of this review in Trade-A-Boat #253, May / June 2015. Why not subscribe today?

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