The Man from Yuma (A Lassiter Western #3‪)‬

Lassiter was bumming a ride on The Caprice Queen when a bunch of river pirates blew the riverboat out of the water and got away with a hundred thousand dollars in gold. He decided to make the dynamiters pay for the inconvenience, and a hundred thousand - thewhole bundle - was the figure he decided on. Getting it wouldn't be easy, but in the end, Lassiter always got what he wanted.