Seakeeper

• Category: gyroscopic anti-roll stabilisers and vessel attitude control
• Founded: 2001 by Shep McKenney and John Adams, with the first workshop at Solomons Island, Maryland in 2002
• Owner: Madison Industries, which acquired the company in 2018
• Manufacturing: Leesport, Pennsylvania, in a facility opened in 2022
• Milestones: first prototype on a 43 foot Viking in 2006, first production contract with Azimut in 2008, ten thousandth unit in 2020
• Range: fourteen models from Seakeeper 1 to Seakeeper 40
• Seakeeper 1: boats of about 7 m to 9 m and up to 5.5 tons, USD 17,400
• Seakeeper 26: boats of about 21 m to 26 m and up to 75 tons, 1,431 kg, USD 268,600
• Seakeeper 40: boats of 26 m and up to about 115 tons, 1,848 kg, USD 365,400
• Roll reduction: up to 95 percent, in the company's own figures
• Spool-up: about 40 to 43 minutes to full stabilisation on a Seakeeper 26 or 40, as published by the maker
• Power: 3,000 W to spool a Seakeeper 26 and 1,375 to 3,000 W running, at 208 to 230 volts

Twenty-five years of one idea

Shep McKenney and John Adams agreed in 2001 to develop a practical modern gyro stabiliser and started work in a garage at Solomons Island, Maryland, the following year. The first prototype went onto a 43 foot Viking in 2006. The M7000 launched commercially in 2008, and the first production contract came from Azimut Yachts in the same year, which is what took the technology from experiment to fitted equipment.

The company sold its thousandth unit in 2011 and its ten thousandth in 2020. It bought its manufacturing partner, Joma Machine Company, in 2008, moved to Mohnton in Pennsylvania and opened a purpose-built plant at Leesport in 2022. Madison Industries acquired the business in 2018. A training facility opened in Tampa in 2021, which matters because installation quality decides whether the equipment performs.

How the gyro actually works

A flywheel spins inside a vacuum enclosure. When the boat rolls, the gyro tilts fore and aft, and that precession generates a torque to port and starboard that opposes the roll. The vacuum is the engineering trick. It lets the flywheel spin roughly three times faster than a conventional design, which cuts its weight by two thirds and halves the power it needs.

The company quotes flywheel speeds up to 9,750 rpm on the smaller units and rim speeds around 557 miles per hour. The large units run slower, at 5,000 rpm on a Seakeeper 26 and 5,150 rpm on a Seakeeper 40, and carry far more angular momentum. A patented glycol and seawater cooling arrangement removes the heat. Control is automatic and reads the sea state continuously.

Forty minutes of spool-up is the price of an anchorage that nobody wants to leave.

The range, and what it costs

Fourteen models cover boats from about 7 m to over 33 m. A Seakeeper 1 suits craft of roughly 7 m to 9 m up to 5.5 tons and lists at USD 17,400. A Seakeeper 6 covers about 13 m to 16 m up to 24 tons at USD 69,600. A Seakeeper 18 covers roughly 18 m to 23 m up to 56 tons at USD 183,700.

At the top, the Seakeeper 26 handles boats of about 21 m to 26 m and up to 75 tons for USD 268,600, and the Seakeeper 40 handles 26 m and above to about 115 tons for USD 365,400. Every one of those figures excludes installation, which on a retrofit can be a substantial fraction of the unit price again.

What it does to life aboard

The claim is up to 95 percent roll reduction, and the number that matters to an owner is not the percentage. It is whether guests stay at the table. A yacht lying beam-on to a swell in an otherwise perfect anchorage empties out by nine in the evening, and the usual fix is to move, which costs the anchorage. A gyro removes the reason to move.

The second effect is at low speed and at rest, where fin stabilisers historically did nothing. Seakeeper works at zero speed by design, which is why it appeared first on sportfishing boats that sit still for hours. On a yacht it changes tender operations, swimming off the platform and whether anyone is seasick in the saloon.

Spool-up, power and the generator

Two operational facts govern how the equipment is used. The first is spool-up time. Both the Seakeeper 26 and the Seakeeper 40 reach full stabilisation in about 40 to 43 minutes, with maximum revolutions taking 70 minutes on the larger unit. A gyro cannot be switched on as the anchor goes down. Crews start it well before arrival.

The second is power. A Seakeeper 26 draws up to 3,000 W to spool and 1,375 to 3,000 W running depending on sea state, at 208 to 230 volts single phase and 20 amps. A Seakeeper 40 needs 5,000 W to spool and 1,900 to 4,400 W running at 30 amps. A generator has to be online whenever the unit is running, and it also needs 4 to 8 gallons a minute of seawater cooling.

Weight, space and retrofitting

A Seakeeper 26 weighs 1,431 kg and a Seakeeper 40 weighs 1,848 kg, in packages a little over 1.4 m square and about a metre high. That mass has to go onto a properly engineered foundation, low and close to the centre of the vessel, and the structure often needs work to take it. There are no fins, no shafts and no hull penetrations beyond the cooling water.

The absence of appendages is the strongest retrofit argument. Fin stabilisers require holes in the hull, they add drag under way, and they can be damaged alongside or in shallow water. A gyro sits inside the boat and can be installed almost anywhere the structure allows. The cost of the installation is the variable, and it is not published.

Where it stops

The ceiling is real. The largest unit is rated to about 115 tons, which is a boat of roughly 26 m to 33 m. Above that an owner is either fitting multiple units or looking at fin stabilisers with zero-speed capability, which is what most yachts above 40 m carry. Anyone with a large displacement yacht should treat Seakeeper as one option among several and not as the default.

The other limit is the sea state. A gyro reduces roll and does nothing about pitch, so a head sea is unaffected. Seakeeper's answer to that is Seakeeper Ride, launched in 2023, a vessel attitude control system for planing boats under way. It is a separate product solving a separate problem.

Service, warranty and bearings

The units carry a multi-year factory warranty and the bearings are field replaceable, which is the single most important design decision for an owner. A sealed unit that had to go back to Pennsylvania when a bearing wore would be a season-ending failure. Field replacement means a technician comes to the boat.

Seakeeper trains installers and service technicians directly, and the network follows the American and European production boat industry, which means coverage in Florida, the Bahamas, the Balearics, the Italian and French Riviera and the eastern Caribbean. Noise output is about 74 dB at one metre on a Seakeeper 26, so the mounting location and the sound insulation around it are part of the specification and not an afterthought.

Against fin stabilisers, and who should fit one

Fin stabilisers from established European makers remain the standard on large displacement yachts, and modern fins work at zero speed. They cost more, they add drag, and they put moving surfaces outside the hull. A gyro costs less, adds weight instead of drag, and is invisible from the outside. On boats up to about 115 tons the gyro usually wins on installed cost and simplicity.

The owners who should fit one are those who anchor out most nights, who eat aboard, and who have guests with no sea legs. The owners who should look elsewhere are those with yachts beyond the size range, those without generator capacity to spare, and those whose boats are only ever used under way in flat water.

Who it is for: Owners of boats up to about 115 tons who anchor out, eat aboard and are tired of moving at nine in the evening because of a swell.