[supercat]

Winner takes all

I simply find it amazing that most of the "winners" wouldn't be mortally wounded.

[Covenantor]

Whose to say they weren't. Remember most of the crews of the target vessels were impressed and likely to join with the depleted pirate crew and sail as freemen under the old Jolly Roger. And some were forced to come along as non-share holders. No looty, no booty.

[Little Ray]

Boarding actions always had very high levels of casualties (assuming your opponents weren't drunk out of their skulls, very common for pirates, or well "prepped" by grapeshot). Read an account of the Bonhomme Richard vs. the Serapis.

However, pirates seldom had to actually fight their way aboard. Most ships surrendered to the pirates when called up to do so. If they did not, the pirates would give them no quarter and kill everyone aboard. Since pirates might cram 120 men and a dozen cannon into a relatively small sloop and the average merchant crew ran about 15-25 men, resistance would be suicidal. (Machine guns have made things a lot more "equal" these days!)

The Queen Anne's Revenge was a fully rigged ship, and carried an armament more appropriate for a frigate and a large crew. The only thing that could survive a fight with it was a naval vessel... Fortunately, Blackbeard scuttled it.