This manual covers Stuart Turner R3M, R3MC, and Model 55 marine engines. These engines are designed for marine applications and are known for their engineering quality and reliability. While specific production years are not detailed, the manual provides comprehensive information for these models. This document serves as a complete service, repair, operation, installation, maintenance, and parts manual in English. It includes detailed troubleshooting support, high-quality, professional-technician-equivalent technical accuracy, and clear, step-by-step, zoomable illustrations. The manual is designed to assist owners, mechanics, and technicians in maintaining and repairing their Stuart Turner marine engines, with service intervals and fluid specifications detailed within.