SEACOCKS - what sealant to use?

mitiempo said:
Yes.

I wonder how many older boats have through hulls with nuts, probably loose by now, and rotten ply in between really only held from turning by 30 year old sealant?
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Gosh, you are a pessimist aren't you.

Its obviously worth checking these things as part of ones maintenance schedule and annual checks, but some boats were built with nuts holding the through hull onto the hull and they are fine.

As it happens our boat was originally built in 1986 and we have lots of through hulls which are parallel threaded with just a nut. However there is a substantial backing plate of marine ply under each one which was usually flowcoated over to seal it when the boat was built.

I have had to move or change a couple of the fittings and they are very tight and nearly impossible to move. The nuts sometimes have to be ground off, and through doing that I know just how strong they are. There is no trace of de-lamination or deterioration in the ply. I have a poke about from time to time, but on the whole I have total faith in the skin fittings we have, and I wouldn't like people reading these forums to get any potential problems with threaded skin fittings fastened by large nuts out of perspective.

It is obviously worth keeping an eye on these things, but there seems to be a groundswell of opinion gathering that says that threaded skin fittings held on with just a nut are wrong. I don't think that the case is made, and I recall that there are some people who also think that ANY underwater skin fitting is the work of the devil himself, and I am starting to put this 'nuts are wrong' argument in the same category. I take the 'no skin fittings at all argument' view with a very large pinch of salt.
 
mitiempo said:
Yes.

I wonder how many older boats have through hulls with nuts, probably loose by now, and rotten ply in between really only held from turning by 30 year old sealant?
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The other answer to your question, is 'How many boats sink on their moorings' or have sudden sea-cock or skin fitting failure?

One hears of the occasional one, but of the many hundreds of thousands of boats in commission round the world, its not making headline news every day because there isn't a major problem with the things. Furthermore, when investigations are done into the very few who have had problems, there are often circumstances that explain the problem. (A poor understanding of galvanic protection, or plastic skin fittings being knocked off by an accident etc etc)

As I mention in my other post, a seaman like attitude to checking these things keeps your boat afloat and the wet stuff on the outside.
 
mitiempo said:
Yes.

I wonder how many older boats have through hulls with nuts, probably loose by now, and rotten ply in between really only held from turning by 30 year old sealant?
Click to expand...

Well mine for a start, although no ply involved just the GRP and not loose but the sealant is the old fashioned Sealastik that was still in use 30 or so years ago.

What I dont like about the IBVF adaptor are the fixing screws countersunk into the hull from outside. I would be happier with bolts or screws though an external plate, similar to the way Blakes Seacocks are fitted.
 
Only box spanner will do.

Only a box spanner would fit.
The nuts are recessed about 1/4” below the inner skin and there is only just sufficient clearance to fit the washer. Nothing other than a box spanner will go near.
The box spanner must also be a full ring. An open C would not be strong enough and would open and slip.

I have 11 skin fittings (too many for my liking) and they consist of:

1 x 1/2” BSP - Propshaft lubrication and cooling.
4 x 3/4” BSP - Toilet inlets and shower outlets (2 heads)
3 x 1” BSP - Basin drains and engine cooling inlet.
3 x 1-1/4” BSP - Toilet outlets and galley sink drain.

Spanners used:-
1/2” & 3/4” BSP's normal double ended plumbers box spanner (sawn in half due to restricted access depth.
1” BSP used an old box spanner from my toolbox about 1-9/16” AF (slightly over 1-1/2”).
1-1/4” BSP was the biggest problem but a Land Rover hub nut box spanner (52mm) did the job.
This also got the old nuts off, one of which was very tight and needed a 2ft lever but showed no sign of slipping.

See photo below of one of my original fittings. This one has the skin fitting, ball valve, R/A bend, hose tail (some others have the bend before the ball valve).
You can also see in this photo that the nut is cracked at the 2 o'clock position, I found 6 of my 11 fittings had cracked nuts, hence my reason for re-fit. (2005, 6 year old Beneteau).

I loose fitted the skin fitting, with the ball valve (or bend) tightened down and rotated the skin fitting to align, then marked the outside flange of the skin fitting with a pencil line to the hull. Disassembled all, then refitted the skin fitting with Sikoflex, tightened the backnuts, whilst my assistant held the skin fitting with the pencil marks aligned from the outside. This ensured that the ball valve (or bend) is correctly aligned when tightened down, with a little sikoflex on the threads to seal.
The next part is the problem bit because the bend (or ball valve) needs to be aligned onto the first part, which means it can't be fully tightened. For these I will use some GAS PTFE tape on the back of the threads (to tighten on to) with a little sikoflex on the start of the threads to ensure a seal and provide some adhesion.

All threads are BSP and parallel (we don't use NPT over here). Although some BSP fittings in taper are available, these are all parallel.
 
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i have only ever used waterpump grease - no sealant. its very thick / viscous, and because the seacocks are always at approx seawater temperature it never becomes more fluid. have never had any problems in the last 6 years. also means you can get the fitting off in the future!
 
I Used Loctite 577

I found this thread useful when planning my seacock replacement, so though it would be worth adding my experience to the end of it.

I bought all the bits from ASAP, except the Loctite 577 which came from RS.

I left the original through-hull fittings in place as they looked fine and the "user manual" for the 36cc says that they are bronze. I worried a bit about damaging things getting the old elbows and valves off the skin fitting, but in the end they all came off fairly easily. I did apply as much heat as I dared with a hot air gun (wrapped everything nearby in tinfoil!) then used a set of pipe grips. I also bought (from ebay) a huge adjustable spanner with jaws that opened to 60mm-ish. That made getting all the old valves off very easy.

I had 8 sets of valves to replace; 5 of them had 90 degree elbows before the valves.

Fitting them was quite a straight forward job, even although I've not done this before. I used back-nuts on all the elbows and on the "straight on" valves, partly for security, but mainly as it allowed the elbows and valves to be aligned exactly as I wanted them. That said, I didn't use lock nuts on the join between the elbow and the valves - the treads were too short.

When assembling it all, I initially did it all "dry". This let me see how many turns each fitting needed to be aligned as I wanted. Then I put a bit of Loctite 577 onto the male and female threads; not too much as it ends up everywhere. I then immediately assembled it all as quickly as I could, including tightening the locknuts.

I found the Loctite 577 did set quite quickly, but I never found it set too fast to get the job done.

I used PTFE tape on the tapered fittings, e.g. hose-tails. I suspect I could have used Loctite, but it was cleaner just to tape them up and assemble them with no time-pressure.

It took me several hours to assemble the whole lot, mainly because I was pretty cautious about ensuring all fitted before committing it to Loctite. I didn't have to undo any, so I've no idea if they'll ever come apart...... hopefully someone else's problem in a few decades!

I was nervous about launching - would they leak? Well, all were water-tight so I would be happy to recommend the Loctite stuff. It comes in a nice "springy" bottle that delivers the stuff cleanly and controlably.
 
Only a box spanner will fit

nigelmercier said:
Perhaps I'm missing something, but I don't see the problem. Screw RA fitting onto through-hull, mark direction of turn. Remove and fit in correct orientation.
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The box spanner is required for the back-nut on the skin fitting. If you look at my previous photo you can see that the nut is recessed in the inner hull lining and so a normal spanner won't touch it. There is no other way to hold the nut.

Of course, if your nut is not recessed then no problem!
 
bonny said:
The box spanner is required for the back-nut on the skin fitting. If you look at my previous photo you can see that the nut is recessed in the inner hull lining and so a normal spanner won't touch it. There is no other way to hold the nut.

Of course, if your nut is not recessed then no problem!
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I still don't see the problem. If you have marked the skin fitting orientation as I suggest, you can fit it before winding on the RA bend.
 
nigelmercier said:
I still don't see the problem. If you have marked the skin fitting orientation as I suggest, you can fit it before winding on the RA bend.
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The skin fitting is retained in the hull by a back-nut, screwed onto the skin fitting against the inside of the hull. This is separate from any bends or seacocks. The nut must be tightened against the inside of the hull, either by holding the skin fitting from the outside whilst screwing on the nut, or by holding the nut on the inside whilst screwing in the skin fitting from the outside. Either way the nut requires a spanner to either turn it or hold it.
Because my hull has in internal lining, this nut sits in a recess about 1/2" deep. This is why a box spanner is needed.

Prior to fitting the skin fitting I dry assembled everything and marked it from the outside in such an orientation that the RA bend could be fully tightened (which I think is what you are talikng about). The nut still has to be fitted, prior to the RA bend and tightened against the hull - in the recess.
 
bonny said:
The skin fitting is retained in the hull by a back-nut, screwed onto the skin fitting against the inside of the hull. This is separate from any bends or seacocks. The nut must be tightened against the inside of the hull, either by holding the skin fitting from the outside whilst screwing on the nut, or by holding the nut on the inside whilst screwing in the skin fitting from the outside. Either way the nut requires a spanner to either turn it or hold it.
Because my hull has in internal lining, this nut sits in a recess about 1/2" deep. This is why a box spanner is needed.

Prior to fitting the skin fitting I dry assembled everything and marked it from the outside in such an orientation that the RA bend could be fully tightened (which I think is what you are talikng about). The nut still has to be fitted, prior to the RA bend and tightened against the hull - in the recess.
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So what is the problem?
 
Personally, I would not be happy with parallel threaded skin fittings with the next component basically loose apart from thread sealant.

As Nigel says, pre-assemble it to establish where the skin fitting must be aligned for the thread to be done up properly, then mount it in the hull at the correct orientation.

A locknut and thread sealant would be OK.
 
Why don't you use a packer on the skin fitting to bring the nut further out and therefore accesible with an open-ender? A bit of plastic chopping board with a big hole in it would do. Sikaflex or other suitable sealant on both sides just to make sure. If you use Sikaflex, you don't have to wind the nuts up until your eyeballs bleed, just nip them up and let the Sikaflex cure for a day, than another little nip and it's done.
 
nigelmercier said:
No I didn't, I just said I didn't see the problem, and I still don't. Sure, use a box spanner, and assemble the RA fitting later, as I said earlier.
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The problem is that with the thro' hull in position, fitting an elbow plus valve is difficult/impossible because there isn't enough room to fit it as it fouls whatever is in the vicinity. If he assembles all the internal pipework first then he doesn't have access to tighten the thro'hull backnut because it is in a recess die to the internal second skin.

(Unless he uses a thick packer underneath the backnut as I suggested above....)
 
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