I was bored so I googled.
Blackbeard was indeed from Bristol, so the accent chosen for him was correct. There were also notorious pirates from Scotland, Wales, Jamaica, Holland, France and Peuerto Rico. I doubt they all spoke with West-Country accents....
(Me, I'm not... in any way intoxicated, Fri 1 Jun 2012, 13:34, 1 reply)

Whilst that may be so
the fact remains that the majority of English sailors in the Caribbean in the C17th will have hailed from the South Coast and South West and the idea that people wouldn't have assumed an accent of that kind as prevalent amongst these sailors until a film of the 1930s/40s, is utter and complete nonsense.

It was certainly an assumption made by RL Stevenson - the FUCKING AUTHOR OF TREASURE ISLAND, who wrote the sailors' dialogue including - but not exclusively - that of Long John fucking Silver phonetically - so it reads like the generic 'pirate' speak.

The statement above is demonstrably bollocks. Unless of course RL Stevenson was a time-traveller who revised his famous work following a trip into the future where he went to the cinema.

Not only Q, but also E and a little bit of D.
( Monty Boyce, My cheese game is strong, Fri 1 Jun 2012, 13:59, closed)

If I put on a Newcastle accent would you know I was being a "generic miner"?
It does follow that because Blackbeard was from Bristol then Stevenson was more likely to pick a West Country accent and it follows that in making the film they'd choose somebody with that accent. All that makes sense.
However, this does not mean that "generic pirate accent" existed before the film.
I am also not convinced that people would think of Pirates as having West Country accents since those in the know would realise they were not even mainly English. So, at the time of pirates, I would expect most people wouldn't have an accent in mind when thinking of a pirate.
(Me, I'm not... in any way intoxicated, Fri 1 Jun 2012, 17:45, closed)