How to Maintain Your Stabilizers


Stabilizer T.L.C.

Want to keep your stabilizers happy next season?
Here’s what you need to do now.

Maybe your present boat doesn’t have stabilizers, but chances are your next one will: Like bow thrusters, both mechanical and gyro stabilizer systems have shrunk enough these days to be feasible for boats from 35-some-feet and up. If you’ve ever endured a rolling, open-sea passage in a midsize trawler yacht, you’ll welcome this news. But what does it take to keep a set of mechanical stabilizers (I’ll cover the gyro-types in an upcoming column) functioning? Will repairs and maintenance tip you off your rocker? What should you do now to keep your fins finning happily next season?

Stabilizer fin

Because of the size and weight of many fins, it’s generally a good idea to get help from the boatyard crew to maintain a stabilizer system.

Most mechanical stabilizer systems today use fins on either side of the vessel to create forces opposite to the direction of roll, thereby damping it. Certain mechanical stabilizers use technology other than underwater fins, however—Quantum’s MagLift system (, for one, employs spinning cylinders that create lift thanks to the so-called Magnus effect, the same phenomenon that affects the flight path of a spinning tennis ball. Some mechanical stabilizers work at rest as well as underway—they often need a bit more maintenance—but in any case, in anything but a flat calm, virtually any mechanical stabilizer system is in constant motion. The fins, cylinders, or whatever, move endlessly to keep the hull level, directed by an array of motion sensors, speed sensors, position sensors, servo valves, and other cool stuff linked together through a sophisticated control box.

Most of these types of stabilizers are engineered to require minimal day-to-day maintenance. It’s not much different from what your engines demand: Fluid levels and pressures need checking, moving parts need greasing, hoses or oil seals can leak, oil filters periodically need replacing, cooling water needs to keep flowing. But occasionally more complex services are necessary, some requiring that the boat be hauled—for these, now might be the time.

MagLift stabilizer from Quantum

The MagLift stabilizer from Quantum swings a spinning cylinder through a range of motion, using Magnus effect forces to offset roll.

Stick to the Schedule

Where do you start? First, cross-reference the maintenance schedule included in your stabilizer operating manual with your ship’s maintenance and cruising logs. Manufacturers generally provide both service hours and real-time intervals for each item, from the most mundane to the complex. Schedules vary from one manufacturer to another: Naiad (, for example, says to change the fin shaft seals at least every three years or 4,000 hours of use, more often if the stabilizers aren’t used at least twice a month. American Bow Thruster ( wants you to do the same on their TRAC stabilizers at least every six years; Side Power ( stipulates seal changes every 12,000 hours (which represents about 3 years of heavy use, according to Side Power); Quantum says every five years or 8,000 hours.

Other major maintenance procedures have similarly long intervals, but all can be involved and costly: For example, shaft seals are easy to replace, but the hard/expensive part is dropping the fins first; you’ll need a trained technician with the right equipment, and the yard’s help for all but the smallest fins. Some fins are attached to the shafts with bolts or other fastenings, and are straightforward to remove. Naiad, on the other hand, uses a different method: The tapered, splined fin shaft fits into a tapered bore in the fin, explained company technician Charlie Egan; it’s a pressed-on fit with no fastenings. Removing the fin demands special equipment: a hydraulic tool to pop the two pieces apart for larger fins, a mechanical puller for smaller ones. Both cases require a skilled technician to do the job.

Voice of Experience

“The systems are pretty much bulletproof,” said Capt. Carl Gwinn, who has been shipmates with stabilizers for many of his 30-plus years of professional service on motoryachts up to 180 feet. “But stick to the service intervals.” Holder of a U.S. Coast Guard 1,600-ton license, Gwinn is currently the captain of a Nordhavn 86 home-ported on the East Coast. The owners of the Nordhavn are serious cruisers, so her TRAC Digital stabilizers get a good workout every year. Capt. Gwinn explained that stabilizer maintenance starts with common sense. Look for leaks regularly, and if you hear squeaks or unfamiliar noises, check them out. 

“Many people neglect the [hydraulic oil in the] cooling system,” Gwinn continued. “You have to keep it clean and functional or the oil gets hot, very hot, so hot you can’t touch the tank.” Indeed, the oil can get hot enough to change the color of the paint on the hydraulic oil reservoir, he added, or even make it bubble. Overheated oil causes other problems besides burned paint, so take steps to ensure your cooling system keeps working properly. Change the raw-water impellers on schedule, check the zincs, and open and inspect the heat exchanger if you suspect problems. Treat your stabilizer system like you do the heat exchangers on your engines, advised Capt. Gwinn, and check the oil temperature regularly.

hydraulic oil cooling unit

The hydraulic oil cooling units on stabilizer systems use a heat exchanger, and must be maintained for optimal system performance.

Keep the Oil Clean

Healthy hydraulic oil should be honey colored. If it’s gotten too hot, it will turn darker, more like maple syrup, according to Gwinn. If the oil is black, it’s been contaminated, maybe by engine lube oil leaking from a bad seal in the power takeoff that drives the hydraulic pump. “This has happened to me a couple of times,” he said. Overheated or contaminated oil must be changed, ideally by pouring the fresh oil from a clean container through a paper strainer in a clean funnel. Change the oil filter element, too. It typically takes a couple of changes to get all the contaminated oil out of a system.

Even if the oil looks fine, most manufacturers recommend having a sample analyzed yearly for contaminants, just like you do with your engine and generator lube oils. Excess wear in the hydraulic pump can introduce metal particles into the oil, indicating it’s time for overhaul or replacement of the pump. Better to find this out now than when you’re halfway to Bermuda.


Some folks distrust technology and want to stick with mechanical devices that are easy to maintain and repair. Almost anyone can figure out paravanes, the cruising powerboat’s traditional means of reducing and even stopping roll. If you’re a Luddite but you want to cruise offshore in comfort, maybe they’re the solution for you. ➤

And change your system’s hoses every five years, advised Naiad’s Charlie Egan, but inspect them yearly. “It’s not a costly thing,” he added, “but you don’t want one to blow.” Overheated oil can break down the hoses more quickly, so they will need replacement before the scheduled interval. “When you replace the hoses, ask the tech if the company supplies a higher-quality hose than the one included with the stabilizer system initially,” suggested Capt. Gwinn. “Some manufacturers provide lesser hoses as standard, with better ones as an upgrade. Always use the best hoses you can.” Check for leaks regularly, even with new hoses; sometimes a badly swaged fitting can leak on a brand-new hose.

The surprising thing is, for such a mechanically complex system, stabilizers are remarkably reliable, and more so if you maintain them correctly. Proper maintenance doesn’t come cheap, especially if it requires special tech experts and fancy tools, but it’s less costly to maintain systems than to repair them. Besides, do you want to be crawling around a hot engine room 500 miles offshore trying to corral a disabled stabilizer, or cleaning up hydraulic oil sprayed from a hose pushed beyond its natural lifespan? To keep things on an even keel next season, give your stabilizers a little TLC now.

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Stabilizer Maintenance Photo Gallery

This article originally appeared in the February 2014 issue of Power & Motoryacht magazine.