This manual covers Mercury Mercruiser MR Stern Drive Units manufactured between 1983 and 1990. These units, part of the MR Series, are designed for integration with various Mercury Mercruiser inboard engines, providing reliable power transfer through their Inboard/Outboard stern drive configuration. The engineering quality of these units ensures dependable performance for a range of marine applications. This comprehensive Full Service Repair Manual in English provides detailed guidance for repair, maintenance, diagnostics, and rebuilding procedures. It includes step-by-step instructions, detailed drawings, photos, wiring diagrams, and essential safety information. The manual is designed to assist owners, mechanics, and technicians in effectively maintaining and restoring their MR Stern Drive Units, ensuring optimal functionality and longevity.