Sealant for through-hulls

[RosieB]

I'm replacing all the through-hulls and seacocks on my boat, due them being who-knows-how-many years old and made of who-knows-what material.

All the new through-hulls are bronze and all the new seacocks are DZR brass.

My question is, what's the best gunge to use to seal these into the hull openings?

I have some 3M 4200 left over from another job, the spec seems good, but not sure it's the correct/best thing.

Does Life Caulk still exist?

All comments/suggestions welcome.

 

[sailorman]

http://www.ybw.com/forums/search.php?searchid=9244422

 

[RosieB]

For me, that link returns "Sorry - no matches. Please try some different terms. "

 

[Tranona]

LIfecaulk still exists but difficult to find in UK. It is a non setting polysulphide and the alternative that is widely available is arbokol 1000. This would be my choice. However many use a polyurethane such as 3M 4200 which would be equally good as a sealant but is also an effective adhesive so may make removal in the future more difficult.

So, your choice.

 

[wrr]

Jewson also do an Evo-Stick one-part polysulphide, it comes in a range of colours and seems to work like Life Caulk.

 

[peteK]

Butyl sealant, the stuff I have been using is butyl strip as have some left over from resealing the windows,keeps for years without drying up and going hard.

 

[Old Bumbulum]

I swear by CT1 from any diy shop.

 

[AndyL]

The makers of lifecaulk said they were opening a shop in Southampton - but I have not heard from them since. I would use Sikaflex 291i

 

[stuartwineberg]

Butyl sealant, the stuff I have been using is butyl strip as have some left over from resealing the windows,keeps for years without drying up and going hard.

Great stuff for windows, not ideal for underwater. Ct1 or pu40 are fine

 

[Graham376]

Sikaflex 291i

 

[Boathook]

I use Arbomast BR butyl sealant for above and below water. No problems over many years.

 

[Poignard]

I swear by CT1 from any diy shop.

+1 for CT1

 

[AndrewL]

+1 for PU40. Available from Toolstation at about £5 a tube.

 

[superheat6k]

Since Boatlife excellent products are no longer available then Sikaflex 291. None of my boats have sunk using the stuff.

But don't just squeeze it on then pul up hard. Thoroughly bed the mastic you choose all around the fitting right up through the hole, then gently pull up leaving a mastic filled gap ~ 2mm thick between the fitting and hull. Leave it a full week before pulling the joint up hard. This allows the sealant to form a gasket and provides the fitting with some flexibility.

 

[Lightwave395]

+1 for PU40. Available from Toolstation at about £5 a tube.

+2

 

[Tranona]

Most of these recommendations are for polyurethane sealants which are essentially similar in properties to the 3M the OP already has, so no need to buy a new tube if he is happy using it.

 

[asteven221]

Although others recommend CT1 I have not had great success with it. After looking at the CT1 video I though wow this stuff looks good, so I bought some to seal between two long strips of teak. The gap was about 2mm. Whilst doing the job a pal asked me what I was using and when I said CT1 and he said he used it on his boat and found it crumbled after being in prolonged contact with salt water. I said to him that all the reports I have seen are very good, to which he replied that maybe they have changed the formula. Maybe, so I plodded on with the job. After a week or so it was obvious the leak was not fixed, which was probably not the fault of CT1, however what I noted was that it did not provide much of a bond to teak. It came off very easily. Far to easily for my liking. I repaired the job later using Sikaflex 291.

I had a leak in the toilet cistern where fresh water was coming through a seal. As I had the CT1 left from the botched repair on the boat, I used that to seal the leak. Unfortunately it didn't work and still leaked, so I put on more. It still leaked, so I just put on loads and loads as it couldn't be seen. And I mean LOADS. Guess what it still leaked. When I had time to do the repair properly, I removed the CT1 which was about the size of a golf ball and found that (like cheap silicon sealer) it had bonded to some of the surface, but other bits of the surface were wet where it had not bonded.

This winter I intend to have all the skin fittings and seacocks replaced on our boat. Would I use CT1 for through hull fittings? No I wouldn't. From what I have experienced it's not as good as the tried & tested stuff like Sikaflex. That's just based on my experience and maybe I have been unlucky. But with through hull fittings, I just wouldn't take any risks.

 

[Humblebee]

Worth asking the makers of the fittings maybe? Blakes or whoever must have some advice to offer.

 

[VicS]

This is the stuff to use:

 

[thinwater]

Since Boatlife excellent products are no longer available then Sikaflex 291. None of my boats have sunk using the stuff.

But don't just squeeze it on then pul up hard. Thoroughly bed the mastic you choose all around the fitting right up through the hole, then gently pull up leaving a mastic filled gap ~ 2mm thick between the fitting and hull. Leave it a full week before pulling the joint up hard. This allows the sealant to form a gasket and provides the fitting with some flexibility.

And more will say this is a terrible idea, since it may tear the bond, creating a leak. Additionally, SIKA takes at least several weeks to cure to full depth in a seacock in cool weather; most likely the inside is not yet cured.

The conventional wisdom has become to simply tighten the fitting.