A boat I am looking at has a couple of opening portlights where the glazing has crazed supposedly due to UV exposure. Is it possible to have these reglazed or is it down to total replacement?
It's very possible to re-glaze, SVB24.com will happily sell you the plexi-glass cut to size (without the the radi in the corners) you just have to trim up the corners.
I cant remember the exact Sikaflex numbers, but you'll need to make sure you get the right "activator" and "primer" to paint on to the plexi-glass and the frame before you use the sikaflex. Try not to do it when it's super hot (+25C) or when it's super cold (<10C) and also remember sika cures based on the moisture in the air so if its very dry leave plenty of time for it to cure properly.
Also don't forget to leave a 3-4mm gap between the plexi-glass and the frame all the way around to allow for expansion/contraction.