This pretty much means two or more crew members are ready to fight. A loggerhead is a type of shot used in cannon. Two iron balls held together by an iron rod. They can be sued as weapons in hand to hand combat as well as used to shoot at rigging on an opposite ship.

When they were used by sailors to settle grudges they were said to be at loggerheads with one another. Another short one for today. Don't worry, I still have some long winded sea stories to throw at everyone.