This manual covers 90 Drive IO Stern Drive units from the 1960s and 1970s, representing early to mid-generation Inboard/Outboard systems. Designed for marine applications, these stern drives were typically paired with inline 4-cylinder engines, offering various displacement and horsepower options to suit different boating needs. Known for their robust construction, these units provided reliable propulsion for recreational vessels of their era. Key features include a single propeller drive unit, transom mount design, and a raw water cooling system, with steering and trim systems varying between cable or hydraulic and manual or power configurations respectively.

This comprehensive service manual provides essential information for the maintenance, repair, and troubleshooting of 90 Drive IO Stern Drive systems, as well as related 60 Drive and 80 Drive models. It details crucial procedures such as drive oil changes, propeller maintenance, gimbal bearing service, and shift cable adjustments. The manual also covers critical components like water pump impellers and lower unit seals, offering guidance on their inspection and replacement. With detailed technical specifications and clear instructions, this English language manual is an indispensable resource for owners, mechanics, and technicians seeking to preserve the performance and longevity of these classic marine propulsion systems.