We pulled out the old ports. Used a putty knife to get off the bronze trim. We removed the cotter pins on the inside ports and because I had removed and replaced two forward facing ports already we could work this two ports at a time.
I tried to get out the glass w/ out breaking it hoping I could use it as a pattern. No good. First I pulled off the rubber gasket. It had hardened up over the last 25 years and I ordered new gasket material from McMasterCarr. They’re the most reasonable for off the wall hard to find products. Once I pulled off the gasket I found these litle screws ( I believe they’re #5 x 40 threads. Carefully I removed the screws breaking only I believe 2 or 3 out of the entire 10 ports. I believe there are actually 6 screws holding on each retaining ring. Once the screws were out I removed the glass and then W or I wire brushed the bronze flanges. I took one port to a glass shop and had them make some glass inserts w/ the safety layer between the glass. We made some extras glass inserts just to make sure. Putting them back together we used Silicone. Now I know a lot of boats find silicone objectionable, however silicone is one of the best sealants there is. How many aquariums has anyone discovered to leak? However silicone isn’t the best adheasive. However; on the ports they glass is mostly held in by the retaining ring that is screwed down and when installed with the gasket material and dogged down there is nothing that will get the glass out other than breaking through. So we used black silicone and sealed the glass in, replaced the retaining ring, added the gasket and then reinstalled them. What a difference! We can see clearly now.