Dead Reckoning — P.X. Duke

Harry has a problem. In a cantina on mainland Mexico, he picks up a bag that doesn't belong to him. To escape the rightful owners, he steals an airplane and heads across the Sea of Cortez to the Baja. While hiding out under a palapa on an isolated stretch of beach, two mysterious gringas show up in the darkness of night. Unbeknownst to Harry, all three of them are in the same boat-literally-and they end up being chased up the Baja by bad guys intent on recovering stolen property.