In a short story entitled The Last Cruise of the Judas Iscariot by Edward Page Mitchel, Captain Cram, a sailor in Main, builds a schooner with three masts, which is considred by the town's people as a bad omen.
It happens that the schooner runs into many accidents whenever it sails, causing a great deal of damage to its owners. That's why Captain Cram decides to change its name to Judas Iscariot to represent its demonic soul. By the end of the story, Captain Cram is telling its story to a stranger and its last journey, when he has loaded it by stones from the fence of his pasture, probably to make it drown.
He tells the stranger:
Did yer suppose she'd sink in deep water, where she could do no more damage?
No, sir, not if all the rocks on the coast of Maine was piled onto her, and her hull bottom knocked clean out.
I can't understand what he means by "her hull bottom knocked out"?
I searched for its meaning as an idiom and as individual words but couldn't find any sense of it.