Lucky for me, the Beckson ports had been installed with butyl tape and a double sided foam weather stripping, and not one of the high tenacity polyurethane sealants like 3M 5200. All I needed was to pry the trim rings off the cabin sides and then apply a constant pressure to slowly stretch the butyl and remove the ports.

I used my heavy duty putty knife, that I have properly dulled, so I don't scratch the cabin sides.

If your ports were installed with 3M 5200 please be very, very careful removing them. The tensile strength of 5200 is 700 PSI and the fiberglass to gelcoat bond is roughly 400-500 PSI. What this means is that if you try to force the ports off the boat you can literally tear the gelcoat clean off the substrate. In my opinion, garnered over many years of removing this stuff, 3M 5200 has no place on a boat! Use 5200 at your own risk and remember NOTHING ON A BOAT IS EVER PERMANENT NOT EVEN A KEEL!!
If you're at a loss with 5200 try products such as De-Bond to soften it. Sometimes heat will help to soften the 5200 but do be careful using heat guns. They can burn the gelcoat if not used carefully, at safe temps, and kept moving at all times.