The Dividing - Jeff Gulvin

It's 1946, the war in Europe is over and John Quarrie has just left school. Godson to the most famous Texas Ranger in history, he's on his way to spend the summer with his grandma. No sooner is he off the bus, however, than he comes across Pious Noon and Willow Flood, and so begins their adventure. A terrible summer storm, an inheritance forfeited, two corrupt sheriff's deputies, and a terrifying boat trip across The Dividing.
Morgan Barra Junior has been cheated out of what he thinks is rightly his and with gambling debts he cannot pay, he will stop at nothing to get what's due. But he hasn't accounted for Pious and he hasn't accounted for John Q. With murder on his mind, those two boys are all that stands in his way.