Not really chain plates
You really don't have to touch the chain plates, but the covers where they go through the deck, they leak! They are usually held in with pop rivets. Use a small nail and knock out the end, then drill through the pop rivet. Then you can lift and clean under the covers, and around the chain plate. 5200 works great, and lasts for years. Now beore sealing the chain plate covers, step your mast and tune the rigging. This way you do not crack the new sealant you just did all this work to replace, the first time you step your mast. Put the sealant around the chain plates and around the pop rivet holes, set the chain plate covers back where they go, and I just use stainless screws through the chain plate covers in to the old pop rivet holes. Don't tighten down too much. You want to leave sealant between the covers and the deck. Quick clean up the mess before it dries. Most sealants will clean up with water untill they set. Some require acetone. This usually is the biggest deck leak on these boats. The other leak, that is a real pain to fix is a deck to hull joint leak. Lets hope you don't have that one. The windows tend to leak on some of the older ones too. Make sure to rebed all your through deck hardware too. Good luck.