The Curse of the Mystery Mooring Chain

Every mooring, in even the snootiest harbor, should be regarded with a skeptical eye.


Perhaps this has happened to you. It has been a long passage. After several nights of little sleep, followed by a long and tricky entrance into an unfamiliar port, you finally wind your way into the anchorage. You recognize a few friends, make a short tour around the anchorage and there it is — an empty mooring ball! You pick it up the mooring pendant, secure it to bow cleats or samson post, and call it a day. Too exhausted to even put on the sail covers, you collapse in your bunk.

A few days pass, the boat’s tidy again. A couple squalls blow through – nothing dicey, but enough to make you wonder exactly what it is your precious home is tethered to. On goes the mask, the snorkel, and you follow the chain down to find – oh dear. The so-called chain is pencil thin, or a ball of rust, or connected to an old tire rim. In other words, its a disaster waiting to happen.

Look closely at the photo above sent by reader John Stone. This is just one of several links on a “mooring” that was keeping a neighbor’s boat from drifting away. Luckily, Stone was able to get down to inspect it for the owner, whose boat almost surely would have broken free in steep chop. We’d like to say this is a rare occurrence, but it is not—especially when you get off the beaten track and find yourself in unregulated mooring fields where the law of the jungle prevails. We’ve seen moorings like this in even “high-end” clubs, and for anyone who is familiar with our dozens of anchor chain tests over the years, this may come as no surprise.

Many readers will recall that we began a series of mooring chain tests back in 2006, with corrosion reports in 2007 and in 2008. As one Practical Sailor tester put it, the test could be described as an attempt to determine how long it took our hard-earned money to turn into a pile of rust. (As it turned out, this happened a lot faster than we expected.) One particular galvanized mooring chain—an unidentified 5/16-inch “proof coil” made in China—had corroded to nearly as thin in the one above after 2.5 years.

At the end of 2.5 years in the water, when we decided that no one in their right mind would trust their boat to any of the seven badly corroded 5/16-inch chains, we pulled them out for the final inspection. We found varying levels of corrosion, with 20 percent less metal remaining in cheaper Asian-made links, as compared to the chain we eventually recommended from Acco (a brand that has since been purchased by Peerless Chain Co.). The Acco Grade 30 chain, in our view, seemed to be the best balance of price and corrosion resistance in a mooring chain.

The Curse of the Mystery Mooring Chain
Mooring chains are raised for inspection during a Practical Sailor test.

After that report, the chains got shuttled from our test site in Connecticut to our newer headquarters in Sarasota, Fla. There, using sophisticated equipment at a Tampa, Fla., facility that specializes in testing industrial cables, wire, and hardware, we applied increasing loads to our mooring chains and recorded the load data (tensile strength) until they broke.

Most startling was what happened to the stainless steel chain. Even though our stainless-steel chain sample clearly had more meat and was much shinier than our other samples at all stages of the test, it was one of the first to go in our test of breaking strength. The ease with which it broke was shocking, although we can’t say we were totally surprised.

For years, we’ve been warning sailors about the hidden dangers of stainless steel in mooring chains, lifelines, chainplates, anchor swivels, turnbuckles, rod-rigging, keel bolts-the list goes on and on. In many of these cases, we have not rejected the material, merely advocated careful selection of the appropriate grade (304, 316, 316L, etc.) and frequent inspection. Stainless steel remains the most practical choice for many other applications.

Although stainless steel is well-suited for fabricating a wide range of sailing hardware and equipment, we feel that it is a poor choice for anchor or mooring chain-and not just because it costs so much more than the usual choice, galvanized steel. One of stainless steel’s biggest vulnerabilities is the work hardening caused cyclical loading, the repeated “shock” loading that an anchor chain experiences. In simple terms, work hardening makes the metal brittle. Another vulnerability is crevice corrosion, which I wrote about previously.

Here’s what we said about stainless-steel chain in 2007: “Corrosion is just one of the factors affecting a chains integrity. With stainless steel in particular, disregarding work hardening under real mooring and anchoring loads involves a serious leap of faith. Stainless steel sees so little use in high-load-cycle applications precisely because it does not hold up as well to this use as do materials with higher ferrous content. Its ever-shiny surface can actually be a disadvantage, revealing no clues to impending failure.” (See “Marine Metals,” February 2007).

Bottom line: When it comes to anchor or mooring chain, what you can’t see can hurt you.


Darrell Nicholson
Practical Sailor has been independently testing and reporting on sailboats and sailing gear for more than 50 years. Its independent tests are carried out by experienced sailors and marine industry professionals dedicated to providing objective evaluation and reporting about boats, gear, and the skills required to cross oceans. Practical Sailor is edited by Darrell Nicholson, a long-time liveaboard sailor and trans-Pacific cruiser who has been director of Belvoir Media Group's marine division since 2005. He holds a U.S. Coast Guard 100-ton Master license, has logged tens of thousands of miles in three oceans, and has skippered everything from pilot boats to day charter cats. His weekly blog Inside Practical Sailor offers an inside look at current research and gear tests at Practical Sailor, while his award-winning column,"Rhumb Lines," tracks boating trends and reflects upon the sailing life. He sails a Sparkman & Stephens-designed Yankee 30 out of St. Petersburg, Florida. You can reach him at


  1. I have come adrift on unknown moorings three times: 1) on a government-provided mooring in the San Juan Islands (fortunately, shortly after we picked it up, still daylight, no damage); 2) a private mooring in St. John River, NB (dragged the mooring half a mile during the night, fortunately not hitting anything); 3) a government-provided mooring in Calais, France (came adrift at night in high winds, woke when the boat crashed into the harbor wall). I am very skeptical of unknown moorings.

  2. Yes, it’s a bit of a dilemma, particularly if it is not practical to dive it. Choices: A. good luck, trust it B. Put an anchor down as back-up. (Not allowed in some fields, and often leads to tangles.). C. Back up hard on it, and even shock load some. None of them as good and diving it or just not using. Unfortunately, it is becoming a trend to require mooring fields. Government or not, hi-end yacht club or not, it’s a crap shoot!
    I backed down on one once that broke! Hadn’t even shock loaded it. I always prefer to anchor when possible. Particularly in the New England area there are a lot of harbors that will not allow anchoring. Just moorings that you pay plenty for.

  3. Most mooring in the US are privately owned. If you pay a fee, then the owner is responsible for providing a safe mooring. The American legal system gives mooring renters plenty of incentive to provide proper maintenance.

    If you own your own mooring, you are fool not to have it professionally inspected every year.

    In over 30 years of sailing in New England, I have never had a mooring fail. Most of the popular harbors here have no anchoring space.

  4. I have kept my sailboats on a private mooring since 1995 here in Puget Sound. Since first deployed I have kept detailed records on the maintenance I have performed religiously every three years. The most important things I have learned is: 1) Use the largest shackles for the size of chain used because they are the weakest item. Specifically, the threads will rust first, then the pin slides out and whatever is attached floats away. 2) Tighten the schackle pin as much as you can and “mouse it” (secure pin with stainless steel wire). I recommend the use of an appropriate caulk or threadlocker as well. 3) Over time sea growth will build on the chain or line creating a living cantenary and increasing the weight the buoy is supporting. Therefore, use a buoy of sufficient buoyancy. 4) Secure the boat pennant to the chain under the buoy not to the buoy.

  5. Mooring fields are bad news. Plus expensive! I have all kinds of horror stories in my circumnavigation.
    Never pick up a mooring. I use a100 pound anchor and all chain and I consider that the minimum. You must have a power wind last with manual override. I have never drug with that combo!!

  6. I have a mooring in a remote cove in Alaska and it is a magnet for cruising boats. There is a piece of 1/2” floating poly to easily grab and tie off to temporarily while you fish out the 1” nylon or run your own line through the steel ring on top. Yet i have passed by in my skiff (I don’t charge) and seen 2 boats 45’ plus rafted up together and tied off to just the weak poly line, which I wouldn’t use as a dock line on a boat that size.

  7. There are at least three good reasons for the increasing use of mooring fields:
    1. Anchoring does tremendous damage to coral and growth covered bottoms, and destroys seagrass beds.
    2. A well organized mooring field permits significantly more vessels to safely co-exist within a limited space.
    3. A whole lot of people can’t anchor to save their (or your) life.
    Several years ago at the St. Thomas Yacht Club in the US Virgin Islands we went to a system that does not use chain at all. Only line, with floats to keep the lines off the bottom. The moorings are inspected every other month (half the field each month). The major lines last up to five years, if the floats are maintained. Since that approach, we have only had moorings fail when severe tropical storms have hit without much warning.
    And as a side benefit, the seagrasses have recovered tremendously, encouraging the return of young sea turtles, rays and juvenile octopus.