I read this YA book in the mid to late 70’s. It is definitely NOT Deathwatch or The Most Dangerous Game but it has similarities to both.  A man is being hunted by another man – I think simply because the hunter enjoys it.  I’m not sure if the hunted man has any weapons or vehicle.  The setting may be Africa or the southwest US.  There are a couple of plot twists.  The hunted man meets someone who offers to help him, but then it turns out that person also wants to kill him.  And then in another twist, maybe that turns out to be a mistaken impression. Or maybe the first guy ends up helping the hunted man because it turns out the second guy is the real bad guy.  The question of who he can trust is a big part of the plot.