The Devil's Own Luck by David Donachie
Harry Ludlow, forced out of the Royal Navy, becomes a privateer in partnership with his younger brother James. But for the Ludlows, murder and intrigue take more of their time than hunting fat trading vessels. Harry and James find themselves aboard the Navy's 74-gun Magnanime. In command is a captain with whom Harry has crossed swords in the past. When James is found standing over the body of a dead officer, Harry's feud shifts into the background.