Owning a Mercury Mercruiser Number 4 Stern Drive Unit from the early MCM series (1978-1982) demands precision maintenance and expert care. This comprehensive workshop service repair manual is your ultimate guide to keeping your marine engine performing at its peak—whether you're troubleshooting, servicing, or overhauling critical components. Why This Manual Is Essential: Complete Coverage: Detailed procedures for MCM 120, 140, 165, 470, 485, 898, 228, and 260 engines (serial #4891650-6216686) Step-by-Step Repairs: From drive unit disassembly to power trim adjustments—every critical task explained Professional-Grade Reference: High-quality diagrams and service bulletins identical to dealer technical documents Key Features You'll Use: Instant PDF download—start working within minutes Printable pages for shop use (compatible with all Windows/Mac systems) Vital specs for gear reduction ratios, fluid types, and torque values Transom plate assembly and power steering system diagnostics This isn't just a manual—it's your assurance of proper maintenance for Mercury's legendary stern drive units. The detailed troubleshooting guides alone can save you hundreds in mechanic fees, while precise torque specs prevent costly assembly mistakes. 🏷️ Basic Information Identification Make: Mercury Mercruiser Model: Number 4 Stern Drive Units Years Covered: 1978, 1979, 1980, 1981, 1982 Generation: Early MCM Series 📋 Manual Details Documentation Manual Type: Workshop Service Repair Manual Language: English Format: PDF Delivery Method: Instant Download Compatibility: All Versions of Windows & Mac Required Software: Adobe PDF Reader ⚙️ Engine Specifications Model Range Covered Engine Models: MCM 120, MCM 140, MCM 165, MCM 470, MCM 485, MCM 898, MCM 228, MCM 260 Serial Number Range Serial Numbers: 4891650 to 6216686 Engine Type Engine Type: Marine Inboard/Outboard (Stern Drive) 🔧 Transmission Stern Drive Unit Type: Number 4 Stern Drive Gear Housing Gear Reduction Ratios: Varies by engine model, refer to manual 🔧 Maintenance General Maintenance Service Focus: Service and Repair Fluids Gear Lube Type: Refer to manual for specific type and viscosity Power Trim Fluid Type: Refer to manual for specific type 📄 Manual Content Repair Procedures Major Sections: General Information, Troubleshooting, Drive Unit, Drive Shaft Housing Assembly, Gear Housing Assembly, Transom Plate Assembly, Power Trim, Power Steering, Service Bulletins Diagrams Included: High Quality Target Audience: Do-It-Yourselfer 📄 Performance Engine Power Power Range: 120 HP to 260 HP 📄 Documentation Printability Print Capability: All pages are printable