Best sealant for mast collar through-hull bolts

[PaulMcC]

It's in the title really. I have a small leak which seems to be coming from one of the bolts which secure the mast collar to the deck. I've been looking at butyl tape type sealants but for this I'm going to do the bolt up again damn tight and expect the thickness of the sealant will therefore be very thin. Am I better off using Sikaflex291 or something instead?

PS. Not intending to take the mast collar off and rebed the whole thing, just extract and refil one bolt.

Cheers

 

[Karlos]

Possible solution

Assuming the water ingress is from above along the bolt and not from underneath the collar, are you able to countersink the edge of the hole through which the bolt goes in?

If you are, even if it is a shallow countersink, it should allow some sealant to remain packed around the bolt's shaft and give a better chance of sealing, whether you use either butyl or Sikaflex.

 

[Twister_Ken]

Put a generous dollop of your chosen sealant in place and tighten the bolt lightly. Leave the sealant to cure for a day or two (depending on ambient temperature) and then tighten the bolt firmly. That way the sealant will stay in place and won't be squeezed out on the first tightening.

PS - Assuming the thread title should be through-deck, not through-hull!

 

[PaulMcC]

Thanks - much appreciated. And yes my mistake, the mast is on the top not the bottom!

 

[Highndry]

I used Polysulphide when replacing my forehatch last winter. Bone dry underneath. As Ken says, give it 12 hours between just bulging out the side and full tighten. I got mine from Toolstation and a tube cost me around £10. Obviously hope I never have to use it again but I'd recommend it.