You are right most of the time for English, but today that should be "Arrr! He be the sawbones".

Spain had pirates too, but I don't speak Spanish so had to ask an LLM. It suggested that today in Spanish it would be "Él es el matasanos del barco". Any authentic Spanish pirates who can verify or correct that?

Not a pirate but a Spanish speaker.

Interestingly,

He's a doctor [in general] -> el es médico

He's the ship's doctor [this specific ship] -> el es el médico del barco

He's a ship doctor [generally works in ships] -> el es médico de barco