It looks deliberately written in broken English.
deadlights = head lights?
ampytated = amputated?
Context:
CHAPTER XI.
WHAT I HEARD IN THE APPLE BARREL.
"NO, NOT I," said Silver. "Flint was cap'n; I was quartermaster, along of my timber leg. The same broadside I lost my leg, old Pew lost his
deadllghts. It was a master surgeon, him that
ampytated me — out of college and all-Latin by the bucket, and what not; but he was hanged like a dog, and sun-dried like the rest, at Corso Castle. That was Roberts' men, that was, and comed of changing names to their ships — Royal Fortune and so on. Now, what a ship was christened, so let her stay, I says. So it was with the Cassandra, as brought us all safe home from Malabar, after England took the Viceroy of the Indies; so it was with the old Walrus, Flint's old ship, as I've seen a-muck witb the red blood and fit to sink with gold."
More:
http://www.kellscraft.com/treasureislandch11.html