Smolett remind the pirates of their limitations. what are they?

I'm not sure where exactly you mean. Smollett does address the pirates, Silver in particular, in Chapter 20. After Silver finishes retelling off his demands, Smollett replies with what the pirates' limitations are,

“You can't find the treasure. You can't sail the ship. There's not a man among you fit to sail the ship. You can't fight us....your ship's in irons..."

Luckily for Smollett and the others, they are protected by the fort at the top of the hill.