What is Gulliver's post during his final voyage?

Gulliver is head surgeon on his third voyage.

” at last he plainly invited me, though with some apologies, to be surgeon of the ship; “that I should have another surgeon under me, beside our two mates; that my salary should be double to the usual pay; and that having experienced my knowledge in sea-affairs to be at least equal to his, he would enter into any engagement to follow my advice, as much as if I had shared in the command.”