I got some fixed elliptical porthole windows (Bomar/Pomponette) from great Lakes Skipper. the original ones were getting tired in sealing from water. NO instructional sheet. I called Pomponette and they have none except a generic sheet of use a quality marine caulking between surfaces, single sheet. So i toss this out to you all.

There are a window pane, inner ring, outer ring and trim ring. By playing with these, I came down to this:

Install inner ring first, so it is caulked and go though the hull. It fastens with the tabs, so I would say pull back the rat fur to fasten.

Install the outer ring that slides over the inner ring that protrudes. Caulk around edges, and also around outer ring so when pushed in to the inner ring, all surfaces meet against sealant.

Place porthole on the outer ring against the rubber seal.

Place the outer trim ring on top of porthole window, then when fastened, the trim ring screws will go through the trim and outer ring.

Pics below, and all comments welcomed!

Best,

Tony