Mercury - Manual-Operation - 90-879172268. The Mercury Manual-Operation - 90-879172268 is a factory-issued guide specifically created to help boaters operate their Mercury marine engines safely and efficiently. With step-by-step instructions and comprehensive diagrams, this manual equips users with the knowledge needed for confident engine handling and long-term reliability.. Key Features. OEM-Certified Guide - Published by Mercury for precise, accurate information. Detailed Operating Instructio