Underwater putty recommendations - rather important!

[Dipper]

Tru Design also recommend Teflon tape, but the threads are a pretty loose fit and the surveyor I know gave me the end of a tube of Loctite 5331 which he had used on another boat. I had tried Teflon tape and found that it did not give a reliable seal, but the Loctite did.

I thought the threads were rather loose as well but I thought I had better follow the instructions. I'm sure I saw somewhere where they said not to use sealant on the threads.

I've been down to the boat today and there were only 3 litres of water in the last 24 hours so it seems to be slowing which is a relief and gives me a bit more time to fix it. I couldn't do anything today as I was helping launch our club keel boats.

Following on from the advice given I went looking for CT1 sealant, Milliput and Loctite 55. The builders merchant had none of these but I found Loctite 55 in a plumbers merchant. As I was waiting for my receipt a man behind me pointed to the Loctite and said 'That's excellent but rather expensive'. I told him I was also looking for CT1 and couldn't find any locally and he told me that the electrical factors down the road had it. When I went in there they were having an open day and I bought a tube of CT1 and got a free doughnut. Result! One of the salesmen there was really keen on the CT1 and had used it in damp areas on his house with great success.

My plan is to unscrew the seacock 3 or 4 threads (there are about 8 turns available), coat the exposed threads with CT1 and screw the seacock back on. I'm fairly confident that this will work. If I sink, I'll let you know.

I'd love to try the Seabung but would prefer to do it on someone else's boat first.

 

[KellysEye]

I used Sikaflex when the Marelon seacock was dry after haul out, leave a quarter turn then tighten when dry.

 

[Bobc]

Also, once you've screwed it back up, put a fillet of CT1 around the joint. Once it's dry it won't leak but you'll never get it off.

Best of luck.

 

[Tim Good]

The chap that makes Seabung is actually a friend of a friend. He might give you one if you offer to do a case study with photos. Let me know and I can put you in touch.

Also the valve shouldn't need to be screwed all the way down. Don't you have a backing nut option which allows you to align the handle on the valve. I'd have thought PTFE should be sufficient if you piled enough on there. I think a lot of people just put 1 or two layers and think that is enough.

 

[Vara]

I wouldn't use CT1 or epoxy putty in this application unless you are sure you will never have to remove the valve. Both CT1 and Milliput are brilliant products but will make the joint pretty well permanent. I've used fernox LS Xin this application, 4 years later no ingress of water.
http://www.screwfix.com/p/fernox-ls...pjKx8iY03sZecnGmokQNcjCPFcaOJm9pZGRoCD2Tw_wcB

 

[Dipper]

I used Sikaflex when the Marelon seacock was dry after haul out, leave a quarter turn then tighten when dry.

Unfortunately unless I pay for a lift out, the threads will be wet. I should have used a sealant when I fitted it. Hopefully this thread will save someone else from making the same mistake.

Also, once you've screwed it back up, put a fillet of CT1 around the joint. Once it's dry it won't leak but you'll never get it off.

Best of luck.

I wouldn't use CT1 or epoxy putty in this application unless you are sure you will never have to remove the valve. Both CT1 and Milliput are brilliant products but will make the joint pretty well permanent. I've used fernox LS Xin this application, 4 years later no ingress of water.
http://www.screwfix.com/p/fernox-ls...pjKx8iY03sZecnGmokQNcjCPFcaOJm9pZGRoCD2Tw_wcB

I have yet to remove a seacock for 'servicing'. When they become stiff or suspect I just change them. My main concern is to stop it leaking so that I can go sailing this season. If I have to cut it out next winter, it's not a huge financial loss.

I have used Fernox LSX in the past and if I hadn't had other suggestions I would have gone with that.

The chap that makes Seabung is actually a friend of a friend. He might give you one if you offer to do a case study with photos. Let me know and I can put you in touch.

Also the valve shouldn't need to be screwed all the way down. Don't you have a backing nut option which allows you to align the handle on the valve. I'd have thought PTFE should be sufficient if you piled enough on there. I think a lot of people just put 1 or two layers and think that is enough.

That's really kind of you Northcave but I need to get it done in the next few days. Also I have to say that I'm a little nervous of trying out the Seabung on my own boat! If I could get alongside a wall on a falling tide, I would definitely give it a go. If it works as well as suggested, it would be an ideal solution especially since my seacock and skin fitting are new.

As regards screwing the valve down, the Marelon seacocks are slightly different from normal seacocks in that they DO need to be screwed down onto the backing pad and there is no backing nut on the skin fitting. Once the valve is screwed down, it is secured to the pad with a couple of screws which prevents it from unscrewing.

Thanks for all the comments. Much appreciated.

 

[Dipper]

I'd have thought PTFE should be sufficient if you piled enough on there. I think a lot of people just put 1 or two layers and think that is enough.

I only put one layer on with a bit of an overlap. I'll remember that tip now!

 

[Tim Good]

I only put one layer on with a bit of an overlap. I'll remember that tip now!

I had to put a 90 degree elbow on 1.5" valve last night and it was impossible to do up tightly as it would be misaligned. As the thread is so big and I didn't want it to be loose I put a good 5 layers on. Someone is going to tell me that is wrong now but never had an issue doing it.

 

[Heckler]

I think it's leaking around the thread. With the Marelon fitting, the skin fitting is stuck into the hull with Sikaflex 291. There is no backing nut. The threaded part of the fitting is cut to length as it can fit a wide range of hull thicknesses then they advise using PTFE tape on the thread. The seacock is screwed onto the thread hand tight until it fits flush onto the backing pad and secured to the backing pad with two screws so that it can't turn. I don't think the skin fitting is leaking as I used a generous dollop of Sikaflex to get a good seal. The leak appears to be coming from where the seacock touches the backing pad but until I dismantle the heads, I won't know for sure.

If ive got it right, parallel pipe threads, they seal the thread joint with a fibre washer between the fitting and the thread. If you have cut it then it is probably at a slight angle and isnt coming up tight against the end of the thread. You probably havent got a fibre washer in there anyway.Teflon tape etc only seals on tapered threads. All the rest of the snake oil potions are a bodge! Lift the darned thing out and go back to basics OR go over the side with a wooden bung, wrapped with teflon to help seal, tap it in to the fitting, dont forget you want to get it out, the go back inside and remove the fitting. Then look at it from a mechanical seal point of view. Its my view that there SHOULD BE A BACKING NUT!
S

 

[Billba]

A similar thing happened to me but in my case I was using sikaflex 291 and was a bit mean on the internal thread. I fitted 5 all at the same time and three different sizes, only the 1 1/2" one weeped slightly. I do not know how far yours is below the waterline but in my case I was able to tip the boat sufficiently to expose it. Halyard to adjacent pontoon and winch carefully. I have a 32 foot boat and see yours is 26 so could be possible. Once exposed I was able to reach up from outside and seal between the top of the skin fitting thread and the inside of the seacock. Incidentally the pdf you cited was for the US version not the OEM 93 model which I'm assuming you have. PTFE tape could have worked but it definitely would need more than a couple of layers of wrapping. When I dried out over winter I was able to remove the whole unit, clean it all up and start again. Best of luck whichever method you use. Cheers.... Bill

 

[ctva]

I fitted a Marelon seacock and skin fitting two years ago for the engine inlet with no problems (but with a healthy dose of scepticism). These is no backing nut as the seacock body itself acts as the "nut", hence the need to cut the internal threaded fitting to length. I would possibly susspect that you have not cut off enough to allow it to bed and tighten against the threads.

If you bodge it, you will never be certain that it will hold and may be masking a more serious fault. Use the plug in the end of the handle to seal it from the outside and then dismantle and check. If as you say it's the heads inlet, you will possibly be able to reach it from the surface, but either way bite the bullet.

Good luck and let us k now how you get on.

 

[VicS]

If ive got it right, parallel pipe threads, they seal the thread joint with a fibre washer between the fitting and the thread. If you have cut it then it is probably at a slight angle and isnt coming up tight against the end of the thread. You probably havent got a fibre washer in there anyway.Teflon tape etc only seals on tapered threads. All the rest of the snake oil potions are a bodge! Lift the darned thing out and go back to basics OR go over the side with a wooden bung, wrapped with teflon to help seal, tap it in to the fitting, dont forget you want to get it out, the go back inside and remove the fitting. Then look at it from a mechanical seal point of view. Its my view that there SHOULD BE A BACKING NUT!
S

Stu, I suggest you look at the fitting instructions for the type of Marelon valve Dipper has fitted.
There is a link to the instructions in his post #16 and a video in # 14.

You will see that the backing nut normally fitted to the skin fitting is not used and that there is not one between skin fitting and valve either.

I guarantee you'll not be impressed but at least you will understand Dipper's problem better.... compounded IMO by the use of tape on parallel threads being suggested in the written instructions which he attempted to follow.

Leaving 8 threads ( he says somewhere) may also ha ve been a mistake if the end of the skin fitting then bottoms out in the valve preventing a closet fit between the valve flange and the wooden pad. ( Note 3 screws finally secure the valve body to the wooden pad,)

 

[rivonia]

Only thing to use really is CT-1 Very similar to all the usual adhesives BUT and a big BUT it sticks to wet surfaces. It can be used under water.

 

[Tim Good]

Only thing to use really is CT-1 Very similar to all the usual adhesives BUT and a big BUT it sticks to wet surfaces. It can be used under water.

Isn't it just a case of one manufacturer claiming one thing and the other being safe? I.e. with wind vane pilots Hydrovane says yes mount off center whilst Wind Pilot say no way must be center when in fact they both work off center but just not as well and one brand is happy to say ok and the other won't compromise.

 

[Dipper]

If ive got it right, parallel pipe threads, they seal the thread joint with a fibre washer between the fitting and the thread. If you have cut it then it is probably at a slight angle and isnt coming up tight against the end of the thread. You probably havent got a fibre washer in there anyway.Teflon tape etc only seals on tapered threads. All the rest of the snake oil potions are a bodge! Lift the darned thing out and go back to basics OR go over the side with a wooden bung, wrapped with teflon to help seal, tap it in to the fitting, dont forget you want to get it out, the go back inside and remove the fitting. Then look at it from a mechanical seal point of view. Its my view that there SHOULD BE A BACKING NUT!
S

They ARE parallel pipe threads but there is no washer between the fitting and the valve. In fact, the fitting should be cut so that the cut surface doesn't abut the valve internally because the valve has to be screwed down until it is flush with the backing pad. Then two screws through the valve into the backing pad stops it turning. Consequently you can't have a backing nut on the skin fitting otherwise the valve can't be screwed down fully. The fitting is stuck in with Sikaflex 291 and once the valve has been screwed onto the backing pad, nothing can move. The whole concept is different from standard seacock fittings.

Ideally I would remove the valve, dry the threads and reseal with something less permanent than CT1 but if the valve doesn't leak and it can't unscrew I can't see the problem. It's not serviceable anyway unlike Blake's seacocks for instance. When ashore I can easily poke some grease onto the ball valve if necessary.

 

[Dipper]

Leaving 8 threads ( he says somewhere) may also ha ve been a mistake if the end of the skin fitting then bottoms out in the valve preventing a closet fit between the valve flange and the wooden pad. ( Note 3 screws finally secure the valve body to the wooden pad,)

I don't know for sure how many threads I did leave but after cutting the skin fitting I dry fitted it and it hadn't quite bedded fully down. I removed it and cut a little bit more off and it seemed to bed properly. There is a chance that the fitting is still a tiny bit long but on the other hand, the length may be perfect. If I had used a sealant on the threads I don't think there would have been a problem but as I mentioned earlier, I read somewhere that I shouldn't.

It would have helped if the fittings had come with an instruction sheet but they didn't.

I quite like the idea of the valve being flush with the backing pad, That must reduce any adverse forces on the skin fitting if it is knocked.

 

[Billba]

These are the instructions you should have had with the valve.....

http://www.forespar.com/pdf/93SeriesValveInstallation.pdf

Also a couple of tips if you decide to fit the external bung whilst working inside.

Take with you a method of clearing any antifoul from the inside of the skin fitting as the o ring seal is a tight fit assuming clean surfaces.

To save getting wet a second time you can tie a cord to the eye provided in the bung but it is quite fragile so be careful as you pull the cord.

Cheers... Bill

 

[Dipper]

These are the instructions you should have had with the valve.....

http://www.forespar.com/pdf/93SeriesValveInstallation.pdf

Also a couple of tips if you decide to fit the external bung whilst working inside.

Take with you a method of clearing any antifoul from the inside of the skin fitting as the o ring seal is a tight fit assuming clean surfaces.

To save getting wet a second time you can tie a cord to the eye provided in the bung but it is quite fragile so be careful as you pull the cord.

Cheers... Bill

Thanks for that Bill. Those instructions would certainly have been helpful before I fitted the seacock. I wonder why they didn't come with the two I bought. They came from a well know chandlers but they weren't in their own branded box. I didn't even realise that there was an integral bung in the handle.

It would seem from the instructions that the depth of available thread is the same for all sizes of valve. I didn't get round to fitting my 1 1/2" Marelon outlet seacock so I've had a look at that. There seems to be about 10 threads (max) available so I think that I can safely unscrew the leaking seacock by 5 turns before applying sealant and then tighten it back up. Even if I accidentally removed the seacock completely, I could still screw it back on again. It won't be much more hazardous than removing the log impeller for cleaning.

 

[Billba]

After you have unscrewed the seacock by say 5 turns and applied the CT1 or similar there may be a difficulty as you screw back down. It will depend on how well the mushroom has adhered to the hull. Better if you are able to get to the skin fitting from outside with say a pipe wrench just to help resist it from the torque you will be applying from inside. Did you consider the tipping over suggestion I mooted earlier. I was able to keep mine tipped for a good while which removed all the pressure in more ways than one.

 

[Dipper]

After you have unscrewed the seacock by say 5 turns and applied the CT1 or similar there may be a difficulty as you screw back down. It will depend on how well the mushroom has adhered to the hull. Better if you are able to get to the skin fitting from outside with say a pipe wrench just to help resist it from the torque you will be applying from inside. Did you consider the tipping over suggestion I mooted earlier. I was able to keep mine tipped for a good while which removed all the pressure in more ways than one.

That's a very good point. It shouldn't turn but if it did that would be a disaster. The same problem could arise with a Seabung or if a plug was knocked in from outside. I guess that's the penalty for having no locking nut.

I'm on a swinging mooring so I would have to go into a marina to tip it. Another option is to get her lifted and held for an hour in a travel hoist - £100. Or I could dry her out against a wall. I could use our rather uneven club jetty but the water there is so shallow I'd need to wait for the next spring tides. The greatest range we get here in Portland Harbour is 2.3m.