And here's number four in the Privateersmen mysteries. In this volume, the Ludlows find themselves in the Caribbean, dealing with some strange goings on (murder, piracy, spying).
They also make an enemy of a Royal Navy captain who illegally impresses many of their crew, and spend the book trying to get them back. Pender, Harry Ludlow's servant and the third protagonist in the series, is one of them. His story while he's away from the Ludlows is also a good one (mutiny, murder).