Originally Posted by Cloaked
You're making this harder than it should be.
Get up under the rub rail with a gun loaded with silicon caulking. Cut a small portion of the tip off and look for any place you can get that tip and squirt it full. Run up each side and all around looking for a crack or crevice you can fill... wipe off any excess and let it set overnight. Done deal.
I've seen this issue on many of the older boats and that has always been my remedy. The only way I'd pull the rub rail (too many rivets) is if I were going to split the deck from the hull or was going to replace the rail and the filler. Otherwise, it's as sound as it will ever be, you just need to fill a few open places.
As I can agree always with cloaked - this project took me 4 hours start to finish. The biggest PITA was removing the loose rivets. I used 3m 5200 to re-seal the hull deck seam and then each rivet got a installed with 3M 5200 - hope to get another 17 years on this repair - boat bone dry now. Most water comes on from dripping skiers.
My rub rail was loose in a bunch of places where PO rub something a bit to hard.., not a big job at all. I started on a rainy Saturday night - finished up Sunday morning... but I did mine in the off season.