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Old 16-08-2016, 17:32   #1
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Question Leaky Lewmar Portlights

I have seven Lewmar old standard portlights (about 1998 vintage). They all leak slightly to a greater/lesser degree and I cannot pinpoint the source (see attached pic). Anyone know what the cause might be?

I have disassembled one portlight. The neoprene seal seems ok, the o-ring inside the catch is compressed so I smeared Vaseline on it, cleaned and reassembled. Made no difference at all.

In each portlight, water is visible in the catch rebate for the lowest of the two catches. There is no visible water on the inside of the Perspex or anywhere else. There is what appears to be a weep hole in the middle of the catch, between the two mounting screws. I suspect that's where the water is coming from, which would mean that the exterior seal is failing (the Sikkaflex or whatever), I guess. I have not yet gone so far as to remove the frame. Does that make any sense? Should I remove the frame?
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Old 16-08-2016, 18:18   #2
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Re: Leaky Lewmar Portlights

The culprit is often the seal on the external frame, the one between the two halves of the frame. They appear as narrow lines of "sealant" running across the frame horizontally at the vertical mid line.

The cure is to use a very sharp, thin blade like a scalpel or single edge razor blade to completely remove the existing sealant. Clean the gap as best you can, then mask the gap right to their edges. Then using a caulking gun, force sealant back into the gap, and then using your finger dipped into a suitable solvent, clean the area, leaving only a flush seam of new sealant. Remove masking and let cure. We usually use Sikaflex 291 or Fixtec polyurethane sealant and mineral turps to clean up.

Good luck with it.

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Old 16-08-2016, 18:52   #3
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Re: Leaky Lewmar Portlights

You can always take a water soluble pen & draw a perimeter around the port, so that when it leaks, the marring of the line will give you a better idea as to where the leak is. Then re-draw your telltale line smaller, around the vicinity indicated by the first test. And repeat the process as needed until the leak's source is isolated.

BTW, this isn't a condensation thing, right?
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Old 16-08-2016, 19:09   #4
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Re: Leaky Lewmar Portlights

No, Uncivilized,

It is just the place where those lewmars fail over time. We had the problem, and a boat worker told us what to do. Voila! it worked.

The other aggravating thing they do, imo, is that their sticky-backed velcro that holds on the interior frames fails, too, and you have to locate more to fix those up, there, it's a simple replace.

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Old 16-08-2016, 19:54   #5
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Re: Leaky Lewmar Portlights

I have had some success with my portlights by treating the functions of adhesion and sealing separately.

I've been using the 3MVHB tape for adhesion , though fasteners can do the job, and the Dow 791 for the sealant. I've been less satisfied with products that are touted as adhesives and sealants.
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Old 16-08-2016, 20:55   #6
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Re: Leaky Lewmar Portlights

Ann has it right. I just redid 6 of them on a benny a month ago. You can also pop off the inner trim and get some caulk in the gap between the halves from the inside.

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Old 16-08-2016, 21:37   #7
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Re: Leaky Lewmar Portlights

Thanks everyone! Yes, it took me a while to rule out condensation but no, it is definitely a leak. Just to be clear, Jim, you mean the join shown in the attached photo, I guess?

I just reread your answer and I think I misunderstood. Are you saying to remove the sealant all the way around?
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Old 16-08-2016, 21:51   #8
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Re: Leaky Lewmar Portlights

Just in that crack. Get at it with a pick and it will pull out.

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Old 17-08-2016, 01:32   #9
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Re: Leaky Lewmar Portlights

Quote:
Originally Posted by daga View Post
Thanks everyone! Yes, it took me a while to rule out condensation but no, it is definitely a leak. Just to be clear, Jim, you mean the join shown in the attached photo, I guess?

I just reread your answer and I think I misunderstood. Are you saying to remove the sealant all the way around?
Yep, that's the guilty party in a lot of cases. Looks ok, still leaks. Give it a try, for you have little to loose, and there is a very good chance that it will solve your problem.

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