Preventing water in ply subdeck under teak

[howardclark]

This year I am having to recaulk a lot of seams but over the years where I have real damage to repair is where fittings are through bolted and ply has gone soft.
I have a new cunning plan and am wondering if anyone can point out obvious flaws,
A good example is one I will be repairing this week. The boom gallows is bolted through with 4 M6 bolts each end. At one end the ply is shot and investigation has shown the mastic has failed and rather than water going all the way through ( which would have been seen & resolved) , it has tracked into the ply and I have to replace a 6x8” piece.
The problem is that the wood, mastic and metal all have their own their own reactions to temperature and moisture.
I am not a nerd but do have a 3d printer. I have printed some 8mm sleeves (8mm I/d 6mm/od) in ABS, purchased epoxy which is compatible with plastic, and intend to fit the sleeves into the teak & sub deck. The bolts can then fit neatly through the sleeves, probably just with silicone. The plastic will have far less expansion than the metal, so I would expect any leaks in the far distant future to not get to the ply but to go all the way through thus preventing damage.
Is there anything obviously wrong with doing this?
Thanks in advance for any opinions.

 

[vyv_cox]

Not silicone! It is mechanically poor and does not adhere well to anything. If you used a decent sealant you would not have had any of these problems.

If you have been using silicone you need to remove every trace of it before using something else. Silicones inhibit the cure of many paints and sealants.

 

[howardclark]

The sealant used was sikaflex- doesn’t last for ever. I’ve a joint on the emergency steering position which lasts a maximum 5 years before having to be redone with Sikaflex - but that one drips through onto the wife when sleeping so I am told straight away. There’s no ‘decent’ sealant that lasts forever.

 

[howardclark]

But you are quite correct I will not use silicone on the repair!

 

[Hacker]

Just over size the holes and fill with epoxy, then drill to the correct size. You suggestion increases the number of potential failure points

 

[PabloPicasso]

The best sealant for above the waterline is butyl tape.

Not an adhesive, but seals wonderfully, remains flexible, and can even be reused.

Its fairly cheap too.

May need a different version in hot climates though.

Once you've used it there's no going back. I often make a small countersink under the fitting to give the butyl somewhere to go.

You can mould it into shape you need rather like plasticine.

 

[howardclark]

The best sealant for above the waterline is butyl tape.

Not an adhesive, but seals wonderfully, remains flexible, and can even be reused.

Its fairly cheap too.

May need a different version in hot climates though.

Once you've used it there's no going back. I often make a small countersink under the fitting to give the butyl somewhere to go.

You can mould it into shape you need rather like plasticine.

What make/spec tape do you buy?

 

[Boathook]

What make/spec tape do you buy?

Can't comment on the tape, but I use arbomast br, which is a butyl sealant in a tube. Most chandler's sell it.