The Texians 2: The Horse Marines

Josh Sands was far from his San Antonio station, but the fierce young Texas Ranger had sworn to protect the entire Territory from her enemies—including the Mexican warships unloading arms in the deadly swamplands along the Gulf of Mexico.
The last thing the hard-riding Ranger expected was to be corralled into Captain Isaac Burton’s mad scheme for capturing the warships himself—with a handful of men who had never so much as seen a rowboat.
But Josh had to pursue a private vengeance as well: to hunt down a death-dealing devil known as Cotton Blue; a vicious gunrunner who had killed Josh’s partner in cold blood; killed for the same pleasure other men found in a woman’s arms...