Changing through-hulls between tides?

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LocoLoic

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Yes, I know it's a risky one as it relies on everything all working on the day, otherwise you're looking at some emergency patch-up to plug the hole!

That said, if I were to attempt it, I'm looking for recommendations on sealants that will cure when immersed - sikaflex has a minimum cure time of 24h so I don't think will work.

Thanks in advance!
 
There's a video on YouTube where a guy does a thru Hull in the water using a diver and a softwood plug (and crossed fingers). So it's definitely possible.

Just check if the sealant goes off in water. I think ct1 for example.
 
The hybrid sealants such as CT1, OB1, etc can be applied under water.

The worst skin fitting change I did was due to not being able to hold the fitting when undoing the nut inside the hull. I had to go away and weld up a tool to hold it. If going for a full replacement I would prepare for cutting or grinding the flange off as the fastest method.
 
The goop I used on the last through hull I changed claims to set and even stick underwater, so it can be done. I had a mate who'd change seacocks while afloat, but I think the through hull would be a bit more of a challenge!

With a pessimism born of too many straightforward jobs turning out far from straightforward, I'd be sure to have a roll of Duck tape to hand so you can cover the hole in a hurry should it prove necessary.

vyv_cox said:
If going for a full replacement I would prepare for cutting or grinding the flange off as the fastest method.
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Good idea. Mine was easy - it just came away in my hand :eek: :eek:
 
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Last year about this time on launch I started the engine, burped the Volvo seal, glanced at water coming out of the exhaust, and motored away from the hoist. I had run the engine with hose into Vetus filter before launch with seacock shut. I really thought I was doing it all right.

On launch I opened the seacock, about 5 year old Groco bronze with stainless handle and found that the seacock that fed the engine inlet had failed. Although turned to on position, the actual (brass) ball had stuck OFF. Turning the handle had no effect. Boat was moved to a pontoon about 100 yards away at very low revs with a getting a bit hot engine.

The point is I then put in a new engine inlet seacock using CT1 whilst afloat, though I got rather wet sleeves doing it. The new Groco ballvalve which I fitted has a plastic not a brass ball. No leaks. I'd be happy using CT1 or Screwfix's OB1 for your job between tides. I find CT1 slightly better, but OB1 is OK.
 
We leaned against the harbour wall in Oban and did 4 seacocks and a coat of antifoul over one tide. I used CT1 and had a surplus of bits, lots of spares in case anything broke. The worst bit was waiting for the water to disappear and wondering if she was going to fall over!

 
Thanks all. The *plan* is to just swap out the stopcock which is knackered, but I want options with me in case the through-hull gives out. It's all pretty old.


IMG_6742B.jpg
 
On my last boat I dried out to replace a non functioning depth sounder, it was a like for like replacement. Once the water had vanished I tried to undo the plastic nut but couldn’t. I picked up a large hammer to break up the old transducer tube and was just about to wack it when I thought maybe I’d check the diameter of the replacement, it was larger and I had no hole saw with me. I put back the old transducer in the tube and awaited the return of the water.
 
Looking at the photo your principal problem is going to be getting the old fitting out like as not when you try to undo it the whole assembly will turn so as said above make sure you have a way of either holding the outer flange or are prepared to grind it off. Also as has been said make sure that what you intend to fit is of an appropriate diameter. In case it all goes tits up have a bung and back up plan in place.
The sealant is the least of your worries, there are plenty that will do the job.
 
Yes, grinding off old fitting will be easiest and quickest.

Tek 7 works well under water and is widely available.

I used an angle grinder to cut into a socket to allow it to grip the through hull from the inside while I tightened the nut.

Dry fit and mark the positions of thruhull fitting and seacocks before using sealant.


As already said, have a plan B, bungs tape etc to hand in case.

If it's too nerve racking then get the boat lifted. It might be worth it for peace of mind.

Good luck, and do let us know how you get on
 
Hi all, just to update on this one - thankfully the original through-hull was brass. It was all just furred up and grubby.

The old valve and elbow just unscrewed beautifully. I cleaned it all up, then the new one went on with no hassle. Was a cinch, but glad I had that plan B up my sleeve.
 
LocoLoic said:
Hi all, just to update on this one - thankfully the original through-hull was brass. It was all just furred up and grubby.

The old valve and elbow just unscrewed beautifully. I cleaned it all up, then the new one went on with no hassle. Was a cinch, but glad I had that plan B up my sleeve.
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Why thankfully? Brass is the worst thing to have.
 
I did a seacock in the mud outside Cardiff Barrage .

Itold the lock keeper the plan ,about 30 minutes before Low Water he called us up to let us know the tide was rising early and quickly !

Luckilly the job was done by then.
 
When we bought our first yacht, the surveyor recommended changing all of the through hulls and valves. This meant that we weren't insured until that was done. So the morning of my first day as a yacht owner was a 6am start to dry her out on a wall to do the job.
It definitely dispelled any notion that yachting was going to glamorous. The first one I tried to remove sheared off, leaving a jagged stump of a through hull and a hole through which I could see the mud of the harbour floor below. I discovered a hitherto unknown work ethic as I raced the tide to complete the job.
I also discovered just how good my new friends were as they pitched up with grinders, generators, and various other tools.
Fun in retrospect but not something I'm in a hurry to repeat.
 
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