This service manual covers the Mercury 25 horsepower Big Foot four-stroke outboard motor, starting with the 1998 model year, identified by the serial number prefix OG590000. Designed for robust performance and reliability, this outboard is engineered to provide dependable power for a variety of boating applications. Its four-stroke design ensures efficient fuel consumption and quieter operation, making it an excellent choice for recreational and professional use where consistent performance is paramount.

The purpose of this manual is to provide comprehensive guidance for the maintenance, repair, and technical understanding of your Mercury 25 Big Foot outboard. It details essential procedures, specifications, and troubleshooting steps necessary to keep your engine operating at its peak efficiency and to address potential issues. Owners, technicians, and mechanics will find the information within invaluable for performing routine servicing, complex repairs, and ensuring the longevity and optimal performance of the outboard motor.