This service repair manual covers Mercury MerCruiser 3.7L in-line 4-cylinder engines, specifically marine models MCM 170 MR, MCM 170 ALPHA 1, MCM 165 ALPHA 1, MCM 3.7L ALPHA 1, MCM 190 MR, MCM 190 ALPHA 1, MCM 180 ALPHA 1, and MCM 3.7L LX ALPHA 1. These engines, with a displacement of 3.7 Liters (224 Cubic Inches), are known for their robust engineering and reliability, making them a solid choice for various marine applications. This manual provides comprehensive information to ensure optimal performance and longevity of your Mercury MerCruiser 3.7L engine. The purpose of this manual is to provide detailed instructions and guidance for the maintenance and repair of the specified Mercury MerCruiser engines. It includes information on general procedures, maintenance schedules, troubleshooting common issues, engine mechanical systems, starting and ignition systems, charging and fuel systems, cooling and exhaust systems, and more. With detailed illustrations, step-by-step instructions, and diagrams, this factory manual is an invaluable resource for both do-it-yourself individuals and experienced mechanics seeking to maintain and repair their vessel's power unit effectively and economically.