Seacock Lubrication Tip


The ice has finally gone out of our inlet here at Base Camp and we are getting Morgan’s Cloud ready for launching. Here’s a neat tip that my friend Bob (a fellow charter member of the anal retentive boat owner’s club) taught me.

Why You Should

Metal seacocks should be lubricated every year before launching. If you don’t grease them they will eventually seize up, and since Mr Murphy is always in charge at sea, you will find that state of affairs when you try to close the seacock after a large water hose ruptures.

It’s even worth lubricating the relatively new “maintenance-free” seacocks—those with teflon mating surfaces. Why? Well teflon (PTFE) is also manufactured with oil imbedded as an additional lubricant, but that’s not what they use for seacocks. The point being that if teflon is good, greased teflon is better.

Even if your seacocks don’t seize up, if you don’t lubricate them they will eventually stiffen up so that when working them open and closed you will be putting a huge load on the mating surfaces where the actuating shaft (that connects to the handle) and the ball bear on each other. Eventually, slop will develop in this area and the ball won’t fully close-off the seacock—a scary problem since we might assume a seacock is closed to the deep blue when, in fact, it’s not.

As an aside, the seacocks on a lot of older boats have this problem, and so we should all check for it regularly and look carefully. We have had to replace two seacocks on Morgan’s Cloud for just this reason, that looked and worked fine on casual inspection.

The Hard Way(s)

OK, now we know we have to lubricate, but how exactly do we go about doing that?

Sure we could pull the hoses off to lubricate the ball by squirting a spray lubricant in with the seacock closed…lots of luck with that. Ever tried getting a large hose off a tail pipe it’s been clamped to for even just a year? Good way to burst a blood vessel.

Or we could squirt some spray lubricant in from outside, but it will drip all over our boat’s newly painted bottom.

Worse still, some spray lubricants contain solvents that will dissolve bottom paint. How do I know this? Well, it wasn’t pretty, and resulted in a lot of sanding and repainting.

And anyway, spray lubricant won’t last long.

Some seacocks have a plug you can remove—ostensibly there for draining, which is, if you think about it, a pretty useless “feature” for most of us since said seacock will drain when you open it. But you could temporarily replace said plug with a zirk fitting and use a grease gun. What a hassle.

The Easy Way

Or you could do it Bob’s-Easy-Way:

  1. Close all the seacocks.
  2. Paint the balls from outside the boat with Lubriplate 130-AA grease, which lasts great underwater, using an acid brush (see photo above).
  3. Work the seacock through its entire travel a few times.
  4. Repeat as necessary.

The above process is faster and easier with two people, one working the seacock from inside the boat and the other outside the boat painting the balls.

One caveat: If you have the old fashioned seacocks with the tapered cylinders, you should probably completely disassemble them for service every three years or so since they depend on a clean well-greased mating surface on the cylinder and casing to remain waterproof. Having said that, Bob’s trick will work fine for the interim years.

Thank you, Bob.


Do you have any cool pre-launch maintenance tips? ‘Tis the season, at least for us northern residents. Please leave a comment.

Like what you just read? Get lots more:

Meet the Author


John was born and brought up in Bermuda and started sailing as a child, racing locally and offshore before turning to cruising. He has sailed over 100,000 miles, most of it on his McCurdy & Rhodes 56, Morgan's Cloud, including eight ocean races to Bermuda, culminating in winning his class twice in the Newport Bermuda Race. He has skippered a series of voyages in the North Atlantic, the majority of which have been to the high latitudes. John has been helping others go voyaging by sharing his experience for twenty years, first in yachting magazines and, for the last 12 years, as co-editor/publisher of AAC.

47 comments… add one
  • Dick Stevenson Apr 26, 2015, 12:41 pm

    Hi John,
    Good suggestions in part because it is almost exactly what we do. The difference is Ginger sprays our grease in from the bottom while I work the seacock, the former being what you advise against. I believe in the US we were able to find a spray Lubriplate, but over on this side of the pond I have settled for CRC White Lithium Grease which has seemed to work fine. It does dribble a bit so I only do the spray after the bottom paint is done and dry. The dribble has not affected my bottom paint (usually Micron) in any noticeable way. In any case, I see no reason that spray grease, well worked in to a moved back & forth seacock, should not last as long as a brushed on grease, similarly worked in (maybe spray Luibriplate is less thick?). That said, brushing sounds likely to be more thorough and less messy with over-spray.
    My best, Dick Stevenson, s/v Alchemy

    • John Apr 27, 2015, 7:53 am

      Hi Dick,

      I based my distrust of the longevity of spray lubricants on a combination of experience (that’s what I used to do) and the testing by Maxprop who have found that Lubriplate 130AA is the only grease that lasts in their propellers without washing out.

      Having said that, of course there maybe other greases (including sprays) that I and Maxprop have not tried that work well.

  • todd Apr 26, 2015, 4:31 pm

    Doesn’t this just lubricate the half that’s exposed to the outside while leaving the inside half unlubricated?

    • Marc Dacey Apr 27, 2015, 12:29 am

      That’s what the back-and-forth is for. The action puts the greasy part of the ball on the inside mating surface, and some will get on the other side with enough action.

      I also use lithium grease. I will switch to Lubriplate for salt water as it appears more tenacious.

    • John Apr 27, 2015, 7:55 am

      Hi Todd,

      As Marc says, working the seacock several times seems to distribute the grease well. If the seacock has not been lubricated for years, it’s probably worth painting the ball several times and working it half a dozen times between each painting.

  • Todd Apr 27, 2015, 12:57 am

    Marc, it might just be the model of Groco seacock that I have but mine only allow 90 degrees of motion on the handle so there’s virtually no overlap.

    I’ve also not figured out a better solution than painting the outside with grease so that’s what I do too.

    • John Apr 27, 2015, 8:05 am

      Hi Todd,

      That got me thinking, so I just sketched it out and with 90 deg of handle movement there is about a 60 degrees (rough guess) of overlap of the two sides of the ball. I think that should be enough to distribute the grease as long as you work it enough.

      I also have two of the new Grocos (the replacements mentioned in the post) and they seem to benefit from this treatment in that they get easier to operate after it and my old Grocos (no teflon) get way easier.

      • John Apr 27, 2015, 9:07 am

        Hi Again Todd,

        Just looked my diagram again after I had had by morning tea (always smartens me up) and realized I was wrong, the overlap is probably only 20 degrees or so, so your worry is at least partly justified.

        See Eric’s comment for a good solution.

    • Eric Klem Apr 27, 2015, 8:40 am

      On some seacocks, you can actually get them to turn a full 360 if you remove the handle and use an adjustable wrench instead. If you look at how they are put together, the stops are usually built into the handle.


      • Todd Huss Apr 27, 2015, 2:06 pm

        Eric, great suggestion! My solution has been to fully open and then close the handle ever so slightly. I then reach a brush up to get some grease on the leading upper edge (the inaccessible side) of the ball in the hopes that the closing action will spread the grease on that side.

        However, it’s always bugged me a little knowing one side is properly greased and the other is very slightly greased (but not enough to remove the hose from every seacock). You’re absolutely right that removing the handle will allow a full range of motion to do the entire job from the outside of the boat!

        • John Apr 27, 2015, 3:03 pm

          Hi Eric and Todd,

          Thanks for sorting that between you. It’s very rare these days that I put up a post that you members don’t improve on in the comments.

  • pat synge Apr 27, 2015, 7:17 am

    I suggest using Silicone Grease.
    I’ve always used the Molykote brand (others may be just as good) which is extremely water resistant and tenacious. It’s also useful for O-rings, sail slides and all sorts of other things.
    Good stuff to have on board.

  • Westbrook Apr 27, 2015, 1:46 pm

    I developed a corollary to my law: “If anything can go wrong, it already has: you just don’t know about it yet.”
    Westbrook Murphy

    • John Apr 30, 2015, 9:48 am

      So true!

  • Patrick Genovese Apr 29, 2015, 2:05 pm

    Any suggestions on alternatives to Lubriplate for us on the other side of the pond ? 🙂

    What about marelon sea cocks.. I’m thinking of changing some of my seacocks to marelon.

    • John Apr 30, 2015, 9:25 am

      Hi Patrick,

      I’m sorry I don’t know about a European equivalent for Lubriplate 130. Anyone else have any ideas? The key is that it needs to be not too viscous (so it spreads around) but still tenaciously water proof.

      As to Marelon. We have two of them. To date I have never found any need to lubricate them at all. There are some installation issues though, see this post.

      Also be aware that there are two lines of Marelon seacocks, the consumer line, which are junk, and the OEM line, which are what we have and are very good, albeit with the caveats and installation hassles detailed in the above post.

      • pat synge Apr 30, 2015, 8:46 pm

        Hi John
        Why do you refer to the ‘consumer line’ of Forespar seacocks as being ‘junk’?

        I’ve inspected dozens of boats with these seacocks and, despite the stories, have only ever seen one that has failed. The handle broke – probably because the valve was never opened/closed and had consequently seized and was then forced. I’ve come across many that were stiff to operate but then most people don’t maintain (or even use) their boats correctly. I would like to think that most AAC members are not in that category.

        Forespar seacocks may not be foolproof and you probably shouldn’t stand on them but the vast majority of seacocks are located in spots where you would have to a contortionist to do so (though with a claimed tensile strength for Marelon of 27,000 psi they should not be much less strong than the equivalently dimensioned bronze fitting).

        Yes, like any other valve they should be greased annually and, ideally, opened/closed occasionally in the interim but in my opinion they are far better than most of the so called “bronze” ball valves I see installed. Many of which I would call junk.

        They may not be the very best but I suggest that they are far from being ‘junk’. At least they have a readily accessible flange to make life easier for the installer!

        • John May 1, 2015, 8:28 am

          Hi Pat,

          You know me, always diffident with my opinions! Still, I stand by that one. I have seen and heard of far too many of the handles on the consumer grade Forespar seacocks breaking off. Also, a simple visual inspection and comparison to the OEM version shows how weak the handle is.

          To me that’s just an unacceptable fail mode and warrants the “junk” designation: a hose blows off, you go to close the seacock and the handle comes off in your hand!

          As to saying that said consumers seacocks are better than a lot of what is out there in the market, I’m sure you right. To me that just means that all of it is “junk”.

          Going cheap on a seacock is like buying a cheap parachute.

    • John Apr 30, 2015, 9:37 am

      Hi Patrick,

      In looking around the Forespar site to answer your comment I discovered that they do indeed recommend lubricating Marelon seacocks and even have their own lubricant that is also supposed to be good for metal seacocks.

      • pat synge Apr 30, 2015, 7:28 pm

        And did you note the price of the Marelon lubricant, John?
        Gold plated!

        This silicone grease will do the job very well (and dozens of others on board as well from battery terminals to sail slides as well). $40 for 400g (including postage if you are in US).

        It doesn’t say it’s suited for marine use, of course. It would probably cost at least twice as much if it did!

        • John May 1, 2015, 8:37 am

          Hi Pat,

          That highlights and interesting boat maintenance philosophical point that you and I clearly differ on. To me $40 is a trivial amount when compared to the total amount of money that it takes to maintain an offshore boat properly. Given that, I will always use the manufactures recommended parts and maintenance items, even though I know that on an absolute bases I’m getting ripped off.

          My thinking is that it only takes one disaster caused by using a generic item to outweigh years of small savings on said generic items. For example, some years ago I used a lubricant spray on some good quality blocks with plastic sheaves. Turned out that there was a solvent in the spray that caused the sheaves to crack over time.

          Not only did that little screw up cost me more money that I spend on recommended maintenance items in a decade or two, it could have caused someone an injury. Not worth it I say.

          • pat synge May 2, 2015, 4:48 am

            You’re absolutely right about being wary of using just ‘any old lubricant’ on plastic and might be interested to know that Synco provide useful information about their lubricants’ compatibilities with a wide range of plastics.


            This why I was suggesting having this specific lubricant aboard: because it is so versatile and compatible with such a wide range of polymers. The fact that it’s relatively inexpensive is a bonus.

          • John May 2, 2015, 6:26 pm

            Hi Pat,

            That’s a good point and highlights another difference in the way you and I approach maintenance: I’m not very good at that kind of research and so generally go with the manufacture recommendation. You are clearly much better a ferreting out a cheeper alternative. Different ways to get to the same result.

    • Alan Teale Jun 1, 2015, 11:09 am

      Patrick, K99 Water Resistant Grease by Morris Lubricants, Shrewsbury, is compatible with plastics. It is widely available in chandleries in the UK. It is recommended by the manufacturer for use in stern tubes., etc.. We use it to pack our rudder tube and we will be trying it in our Marelon seacock. Alan

      • John Jun 1, 2015, 4:36 pm

        Hi Alan,

        That sounds great, thanks.

  • Tim Good May 1, 2015, 6:09 am

    Interesting. The general consensus in the UK seems to be NOT to grease seacocks for fear of attracting dirt that will wear away the ball valve. Then again, a lot of the blogs I read from the US, people seem to be using blakes whilst most boats I see in the UK seem to have standard ball valves screwed directly to a skin fitting.

    I say this with relatively limited knowledge given that you guys have seen a hell of a lot more boats that I.

    • John May 1, 2015, 8:50 am

      Hi Tim,

      I really can’t see the dry is better argument. Over the years I have bought three second hand boats. In all three cases the previous owner had not lubricated the seacocks and in all three cases their operation improved dramatically when I lubricated them, and stayed that way. Also, seacocks are really not cycled that much so I would find it really hard to credit that the ball would wear appreciably.

      Your comment also highlights a distressing trend in Europe to use ball valves instead of proper seacocks like those made by Blake and Groco. This is simply unacceptable and should be banned. Further it shows that the boatbuilders that do this don’t give a fiddlers about the safety of their clients.

      Wait, it get’s worse. Many of those ball valves are made of brass, not bronze, and will fail in as little as five years. Talk about false economy when compared to good quality bronze seacocks that will last for 40 years or more if properly cared for—see the post for a potential life ending problem.

      As I said in another comment, fitting cheap ball valves instead of seacocks is like buying a cheap parachute.

      • Tim May 2, 2015, 4:08 am

        It is an odd one I agree, looking at the differences in practice. But even the likes of Hallberg, Najad, Nauticat etc have been using ball valves as seacocks and they are regarded to employee the best boat builders in the world.
        I agree though, the Blakes style do look the way to go but I have never had a boat with one to compare.

        I haven’t seen a chandlery blindly selling brass seacocks and skin fittings. I think it is commonly known here that it is bronze or DZR brass for a seacock. I suppose the total success of DZR is still yet to be seen maybe?

        • John May 2, 2015, 5:58 pm

          Hi Tim,

          Yes, I know that those builders are now all using ball valves however I’m afraid that I draw a rather different conclusion from this fact: That it reflects the general deterioration of the quality of once great boat builders.

          Also, we all need to be very careful about what is and is not real bronze suitable for underwater use because there ale all kinds of material names that use the word “bronze” but are, in fact, some form of brass.

          I was horrified to learn some time ago that many so called quality boat builders are now calling for the ball valves and through hulls to be replaced every five years, which has got to tell us all something, none of it good.

          The bottom line is that good safe seacocks that will last 30-40 years, at least, exist and there is really no excuse not to use them, particularly in a boat that commands a premium price like the ones you list.

  • Neil McCubbin May 1, 2015, 8:24 am

    We lubricate our marelon seacocks with olive oil
    I am a bit shy of lubricate on plastic, although it works well in our Maxprop

  • Neil McCubbin May 1, 2015, 9:26 am

    Ball valves vs Seacocks
    Agreed 100% that brass is a bad valve material for seawater, whether in a ball valve or the gate valves used by the cheap builders in the past.
    However, ball valves are used widely in industry for fluids dramatically more corrosive that seawater. When buying form an industrial source, the full specs are available and reliable, which is not true for all products in the yacht market.”Seawater resistant bronze” is a meaningless term, for example.
    One issue with most ball valves is that they have NPT female threads (outside diameter tapering), which are unreliable when screwed on the parallel (NPS or BSP) threads on a standard through hull fitting. The unfortunate issue is that the NPT thread fits, and is watertight with some Teflon tape. However, the joint is structurally weak, and is liable to wiggle and leak.
    The solution is to tap the NPT thread out to NPS (easy if you have the tap) or to buy a valve with the proper thread.

    • John May 2, 2015, 8:51 am

      Hi Neil,

      I’m sure you are right that there are ball valves available that will stand up to salt water as well as a proper seacock, but to my way of thinking, that does not alter the fact that using ball valves instead of seacocks is simply poor practice because ball valves don’t have flanges and therefore can’t be properly attached to the hull.

      And the issues with threads that you very properly point out just reinforces my opinion. Why go through all that with a ball valve when you can simply buy a proper seacock with a matching through hull from Groco? Only one reason…cost. And saving money on making your boat watertight is just not a good idea.

  • Wilson Fitt May 3, 2015, 9:03 pm

    Hi John

    I fully endorse going for the best seacocks available, damn the cost. When originally equipping my boat, I went with Buck Algonquin flanged seacocks because they were the stock items at local chandleries and appeared to be good marine quality gear. But in less than a year one of them stuck half closed (the head discharge of course) and over time they all became difficult or impossible to operate. It seemed that the chrome plate on the ball was pitting. I contacted B-A about the first one and they replaced it, but did not provide much of a reason for the failure and my confidence was lost.

    I replaced all the seacocks with Grocos at great expense. Ten years later and without any maintenance whatsoever, the Grocos still operate like new, but being a good ACA disciple I greased them this week for the first time figuring it can do no harm.

    • John May 4, 2015, 6:08 am

      Hi Wilson,

      Sad to hear about BA. I always thought their stuff was a good alternative to Groco. Well worth knowing that it’s not.

  • Neil McCubbin May 4, 2015, 2:04 am

    Choice of seacock depends also on hull material. With wood, and I suspect fibreglass, a good solid bolted flanges give great, and probably necessary strength.
    In our aluminium hull, we have high quality reinforced plastic ball valves, which screw on to the threads of 8 mm thick tubes welded to the 8 mm thick hull. The tubes are same alloy as hull, machined with the appropriate pipe thread. No signs of corrosion after 10 years in the water.
    I am much more scared about corrosion if I used a metal valve than physical weakness of the plastic. That said we installed a structure around each seacock that prevents any large moving object, or foot, from applying a load to the valve.
    I will get some of that silicone grease Pat mentions above, instead of our olive oil lubricant

    • John May 4, 2015, 6:05 am

      Hi Keil,

      Yes, I think you are right in your case, the key being the structure that you have reinforcing the through hull.

      What scares me is seeing a ball valve perched on top of a though hull that is not so supported just waiting for an errant foot to cause gusher.

      By the way, we have had bronze seacocks in our aluminium boat for nearly 30 years without problems. The secret is isolating them from the hull. Having said that, if building today I would either follow your example or use the OEM marelon seacocks.

  • RDE May 4, 2015, 3:38 pm

    Of course a properly designed boat has a sea chest rather than a baker’s dozen holes drilled throughout the boat — typically in the most inaccessible of locations. And with one big valve for closure there is less temptation for the bean counters to “earn” their keep by replacing all the sea cocks with ball valves.

    Of course even a ball valve is better than the sea chest on an Italian motor yacht I once worked on. One of the 4″ diameter engine feed lines had a 1/4″ diameter hole in it which someone had “fixed” by applying duct tape and painting it white.

    • John May 5, 2015, 8:04 am

      Hi Richard,

      A very good point that a sea chest is the ultimate answer…but a distressingly rare one.

  • Mike May 21, 2015, 4:10 pm

    Excellent thread. Just wondering if anyone has concerns about lightning strikes and what they may or may not do on boats with bronze vs. Marelon seacocks? We’ve all heard stories of boats sinking due to thru-hulls being blown out by a lightning strike…

  • Rusty Jun 22, 2015, 4:05 pm

    Will there be a problem with the grease fouling watermaker membranes or filters?

    • John Jun 23, 2015, 8:09 am

      Hi Rusty,

      I never thought of that, and since I have never had a watermaker, I really don’t know.

      One thought: I think I’m right in saying that watermaker pre-filters are designed to remove contaminates such as floating oil, and if that’s right then I guess they would catch any grease from the seacock.

      Anyone else have any idea?

  • Coen Jun 23, 2015, 1:39 am

    Hi John,

    It seems to me that whilst sea chests have advantages, one still has to be just as careful about siting and protecting the fittings/valves that go onto them. I have no experience in this regard, but looking at some of the images on the net, it would appear that these valves too could be dislodged by a forceful bump into them. With the tall narrow sea chests typically seen in the few yachts that have them, would this complicate the servicing and access to the valves? Looks like nothing will substitute for thorough planning and good engineering.

    • John Jun 23, 2015, 8:12 am

      Hi Coen,

      That’s a very good point. Bottom line, no matter how you handle seacocks, you have to do it right and protect them from damage. Having said that, I guess one benefit of a seachest is that if one of the valves on the seachest gets damaged you can always turn off the main valves to the chest while you sort out the issue.

      • Marc Dacey Jun 23, 2015, 2:43 pm

        The equivalent plan on a standpipe would be to thread a strong monofilament or a light wire through those crushable plugs used as “soft bungs”. If a teed-off seacock fails or requires service, a sufficiently sized bung jammed down to the grate end of the standpipe (and secured with pressure from above if needed) should retard water ingress well enough to fix what needs fixing. The alternative for more customary seacocks is to dive on the boat, rubber mallet in a softwood bung if the absence of “ears” allows it, and drive the bung out an opened cock from above. I’ve done this, and it creates a nice fountain effect!

        • John Jun 24, 2015, 8:32 am

          Hi Marc,

          Good thought for standard seacocks, but usually the whole point of standpipes is that they terminate above the waterline so that there is no need to plug them to remove the valve.

          • Marc Dacey Jun 24, 2015, 4:17 pm

            Yes, the standpipe terminates above the waterline, but the tee-offs are below the WL. To swap out or to service one of the seacocks for a) engine raw water, b) head intake, c) A/C circuit or d) seawater to the galley would involve plugging the bottom so I only had to drain the water in the “column”, so to speak, in order to remove, replace or service individual shut-off while still afloat. The upside is only two drain lines out (head and galley) and only the standpipe “in” below the waterline. I’ve seen some boats with a dozen holes in the hull, which I find anxiety-inducing.

  • Robert Snelling May 6, 2016, 9:35 pm

    I used Forespar LanoCote this year (first time); I had to warm it up prior to application as, when cool, has the consistency of beeswax; very difficult to apply. I’m going to try and reapply it once our Nova Scotia weather hits the double digits

Only logged in members may comment: