At level 21, I had a max lock picking of 105, but my lockpicking was only at 90 (from earlier practice). I returned to the Pirate Ship north of Ratchet, thinking I could skill up to my max 105.
Wrongo. Those pirate chests in the ship's cabin are easy to use (just right-click on them, or use the skill icon). But they only took me (sloooowly) to 100. And then they went gray.
I went downstairs to Polly's chest (a separate chest entirely that I'd remembered from the Polly quest earlier). It was not active, had no "gear" to show I could do anything with it. It didn't respond to my lockpicking at all. (And a good thing: I didn't feel like fighting Polly.)
I went out, did a little killing and got up to level 22. Back to the Pirate Ship. Nope, chests still gray, no more experience from picking them. So 100 apparently is as far as the Pirate Ship chests go.
I suppose I'll have to go to that tower (Klaven) where the Poison Quest sends you. Hate that, those guys are tough, and at 22 I'll probably still aggro that guy upstairs who walks near the chest. So I'll have to bring some higher level along to protect me. But that's the only place I can see that will bring me up to my new 110 max level.
So, if you expect to get over 100 at that Pirate Ship, forget about it. And Polly's chest won't be of any use at all unless you maybe still have the Polly quest (and you don't kill her).
Darned shame that there's one lousy locked chest in the whole world you can use to skill up over 100 :-(