They are screwed into the deck.
If you can remove the screws and the plates. It is important they the plate is free to slide on the chain plate. Then remove the chain plate clean everything and reassemble. Use a good product like 3M 4000uv as a bedding material. If you just remove the plate, and seal under it, you are just piling bedding material over bedding material.It will not seal a leak for any length of time. I say the the plate should slide on the chain plate because after reinstallation and retensioning of the shroud/s, the chain plate will move and if it does not slide, it will pull the screws right out of the deck. The plate acts like a sort of stem seal on a water ball valve. The plate puts pressure on the bedding material to seal the chain plate.Chain plates move with differential movement from hull to deck (most production boats). The bedding material should have good adheasion and flexibility.r.w.landau