Mercury Manual-Operator - 90-10201N81. The Mercury Manual-Operator - 90-10201N81 is an official, OEM-issued guide that offers essential operating procedures for your Mercury marine engine. Designed with accuracy and practicality in mind, this manual is a must-have for ensuring safe, effective operation in a wide range of marine environments.. Key Features. Authentic OEM Publication - Written and published by Mercury for complete accuracy and compliance. Comprehensive Operational Guidance - Cover