Replacing fixed plexiglass "deadlights" on cabin

[Ed Shankle]

Jeff,
Went through the same angst when I replaced one of my fixed ports last year. I didn't want to deal with spacers, just wanted to smoothly lay in a good bead of caulk and have it press out consistently around the inside of the port, because you can see it from the outside. Despite some opinions not to, I used the screws and it worked out just fine. Held the port in place and didn't over squeeze out the caulk. Just don't tighten down the screws.
By the way, apologies for the earlier Oz reference. I wasn't paying close enough attention to your information, but noticed this time you are in BC!

Regards,
Ed

[Clay Greene]

One other thing about the spacers - you can see them after the window is installed if you know where to look for them.  I also think they could lead to an inconsistent seal because they could prevent you from compressing the window far enough so that the sealant fills any voids.  So, if I had it to do over again, I would consider omitting them. 

[mregan]

I put spacers in when I replaced the windows.  I used 1/8" thick foam weatherstripping.  I can't see them at all.  I'd be worried if you pushed the window in too far in one spot, you would force all the sealant out and have a thin spot.

[KWKloeber]

I believe an older set of CTY instructions says to cut wooden bows that can be springed between the lifelines and the plexi. 
You don't need or want a ton of force, just to hold it so it cures. 
I'd think about holding the plexi in its vertical position (duct tape strips?) and then you need less horizontal pressure against it.  You defo need spacers of some fashion - the idea is to NOT push out the 795.

[Jon W]

I replaced both of mine last year (or maybe 2019 lost track  ). I used Dow 795 from Sealant Engineering, small foam pads for spacers, and the screws. There is caulk between the foam pads and the edge of the portlight so no leaks. I thought about 3M VHB, and making a jig. I decided it worked fine since 1987, why change. If you reuse the screws make sure the holes in the portlight are slightly larger than the screw to avoid cracking.

[DaveBMusik]

Andy from Boatworks Today on you tube has an excellent video. He suggests using 3M high bond tape which is what I did. The tape provides space for the Dow sealant so there is no squeeze out