I removed the ones on my 76 SeaRay and they had silicone RTV underneath as sealant. I don't know if your boat is the same but that is what I found was holding mine in. My inner trim ring came out easily, it was the outside that was stuck. It could be that yours has sealant that was over applied and is also holding the inner trim in place. I used a razor blade to slide in between the outer trim ring and the hull to cut the RTV. If you try this, careful you don't cut into the gelcoat. It could be that you have a sealant that will loosen with heat and warming it may help (don't overheat and melt something). Generally, RTV won't loosen with heat. Mine came out in one piece but I am replacing them with new ones I found on EBay. You might get lucky and find a replacement set. I did have to trim and fill a little to fit the new ones as they were very slightly different.
You made all good points.
The 1 thing I will add and this is strictly a guess.
Maybe they used something better than silicon or rtv.
Could they have used 5200 or equivalent.
Polyurethane is the good stuff used on roofing by the “folks that know”
I myself wouldn’t use silicone on a boat anywhere unless I thought I maybe wanted to get get in there 1 day. Like an access panel or coffin lid.
Anything I wanted seriously held in place or resistant to sun my personal pick would be polyurethane.
And used liberally almost guarantees something is breaking to get it out or loose.
Sorry for the long spill.
