sealing through hulls

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StevenJMorgan

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I'm in the process of replacing some underwater through hulls - first time I've done this and for obvious reasons I want to make sure I get it right.

Is it the usual trick of banging on loads of suitable grade sealer, crank the fitting up finger tight, wait until the sealer has gone off then torque up?? Trouble I can see with this method is that you will have to try and avoid the 'male' part of the through hull from turning at all whilst cranking up the nut for fear of breaking the seal.

Alternative I guess is to bang on the sealent and tighten up and be done with it. What method does everyone else use??
 
Tec7 , 3M 5200 or sikaflex291 or 292 are the products you should consider. With these sealants, they are so thick that I find just applying and tightening once is teh way to do it. Tightening again is too difficult as the sealant is soo rubbery and has adhesive in it anyway. For bedding windows etc. I think tightening afterwards is recommended for non-setting stuff.

Sikaflex has an excellent brochure on recommended application procedures which you can request from their website. Note that sikaflex and 3M have a use by date, not sure about Tec7 as I haven't used it yet.
 
In the thru-hulls I have used there were two metal inserts on the inside of the thru-hull on the side nearest to the water... if you get my drift. If yours are the same, ask someone to help... we did mine between the two of us... one held a spanner up from the outside to prevent it from turning, and the other cranked it up on the inside.

Personally, from replacing mine this winter, I would rather do them up finger tight, leave to set, and then tighten. The last thing you want is for the sealent to be squeezed out and not do the proper job first time.

Touch wood.... mine (x4) have all been perfect so far without a drop of water coming through.
 
You are right too. I think it depends on the temperature that you apply the sealantand maybe if the sealant is close to its expiry date. If it's cold or old then the sealant will be so think that screwing it tight will be ok. If it's warm or new then do it finger tight, leave for 24hrs then tighten. Be aware that brass fittings will screw up tighter so this is more important on brass fittings than plastic thru-hull which won't take the strain though I did use a pipe wrench but only to get a bit of leverage :-)
 
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