Butyl Tape and Sikaflex

[Tom.B]

1 Is this picture taken from inside the boat? If so, you have not sent any pictures taken from outside the boat.
Outside would be where you would want to seal the portlight, on the outside surface, not on the inside surface. That surface should be uniformly smooth all around the hole into which the portlight fits. Your flange around the outside should accept a butyl tape that will then be compressed as you pull the portlight in with your inside attachment, whatever that may be.

2 I agree with Compass, that not all butyl is created equal. I have used a lot of butyl in various projects. The last time I tried butyl, in replacing glass in main cabin forward windows, I got the BT from the Glass Guy where I got the glass. It was hard and not very sticky, so didn't mold to the shape that I wanted and I ended up using 291 Sika, which worked very well. I asked about the tape after that and learned that a recent re-formulation had a lot of window installers complaining. If your Amazon BT is soft and sticky it should be OK, but if it is hard and not sticky it may be the same as what I DIDN"T USE.

I cannot go though every point here, but if it matters to you, all of this is covered by my previous posts.

Butyl tape will not work in this application, so I am going to use LifeCaulk until a more extensive solution can be done. Currently, time does not allow for it.

Thanks for everyone’s input.

 

[Boatcrazy]

Sika will set up and seal, but if there's any future movement it will crack. We had 2 deck prisms that had been set if Sika....and they both leaked. I was (finally) able to get them out, clean out the hole, and reinstall with Butyl. We used West Marine's product. It's been 3 years, 2 hurricanes, and lots of banging thru big seas....so far NO leaks, and the butly is still soft!