1986 Mercruiser MCM 120-260 Stern Drive Units Service Manual

This 1986 Mercruiser MCM 120-260 Stern Drive Units Service Manual covers troubleshooting, drive units, and related components. Ref: 90-86137 286

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Document Details

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Document Number / Seller:
31523 / Sandra Wright
File Size:
40.30 MB
File Type:
PDF
Language:
English
Pages:
230
Printable:
Yes
Category:
Inboard Engine (Sterndrive)
Last updated / verified
Sep 19, 2025

Models Covered & Key Technical Specifications

Verified Specification Electrical Manual: Inboard Engine (Sterndrive) Official Mercruiser MCM 120, 140, 165, 470, 485, 898, 228, 260 Stern Drives - 1986 Service & Troubleshooting Manual 4 System-Standards Model-Designation: MCM 120, 140, 165, 470, 485, 898, 228, 260 (90-86137 286) // Equipment-Series: MCM Stern Drive Units / Power Trim Logic // Unit-Designations: 1986 Service & Troubleshooting Manual. Assessment-Parameter Technical-Path Calibration-Data
Engine Alignment Drive Shaft Housing 120 Ft. Lbs.
Fuel System Carburetor Adjustment 25 Ft. Lbs.
Electrical Connections Wiring Harness 10 Ft. Lbs.
Trim Limit Switch Electrical Testing 5 Ft. Lbs.
Gear Housing Bearing Preload 125 In. Lbs.
Shift Cable Adjustment Procedure 30 Ft. Lbs.

Documented Holding Capacity: 40 Amp fuses are utilized to protect the electrical system. Mapping Technical Measurement Bounds: Pressure readings up to 500 PSI (35 kg/cm²) ensure proper hydraulic operation. Configuration Universal Circuit Specs: Battery voltage of 12V establishes the baseline for electrical components. Benchmarks Maximum RPM Specs: 5000 RPM is the standard operating limit for optimal performance. Range System Installation Footprint: 228 cubic inches defines the displacement of the engine block. Sequences Prescribed Charge Quantity: 40 Amp circuit breakers are standard for safety functions. Baseline

Professional Workshop Service Manual & Technical Specifications

Verified Specification Electrical Manual: Inboard Engine (Sterndrive) Official Mercruiser MCM 120, 140, 165, 470, 485, 898, 228, 260 Stern Drives - 1986 Service & Troubleshooting Manual #4 System-Standards

Model-Designation: MCM 120, 140, 165, 470, 485, 898, 228, 260 (90-86137 286) // Equipment-Series: MCM Stern Drive Units / Power Trim Logic // Unit-Designations: 1986 Service & Troubleshooting Manual.

Document Overview

This table outlines key assessment parameters, their associated technical paths, and calibration data for Inboard Engine Sterndrive units.

Assessment-Parameter Technical-Path Calibration-Data
Engine Alignment Drive Shaft Housing 120 Ft. Lbs.
Fuel System Carburetor Adjustment 25 Ft. Lbs.
Electrical Connections Wiring Harness 10 Ft. Lbs.
Trim Limit Switch Electrical Testing 5 Ft. Lbs.
Gear Housing Bearing Preload 125 In. Lbs.
Shift Cable Adjustment Procedure 30 Ft. Lbs.

Table of Contents Summary

  • Power Trim System Identification
  • Hydraulic System - External Return Lines
  • Trim Cylinder Tests
  • Electrical System
  • Booster Cylinder

Manual Content Details

This manual documents various systems and procedures related to MerCruiser MCM Stern Drive Units. It details the identification of power trim systems, including electrical schematics and hydraulic system layouts for both "Up" and "Down" circuits. Maintenance hierarchies are structured into detailed sections covering component removal, disassembly, inspection, cleaning, reassembly, and installation for critical parts such as trim cylinders, solenoids, and hydraulic pumps.

Procedures for testing and troubleshooting are provided, covering hydraulic system pressure tests, trim cylinder tests, and electrical system checks. Specific guidance is offered for issues like striking objects with light or great force, and diagnostic charts are included for common problems. The manual also details the operation and maintenance of the power steering system, including neutral, left, and right turn modes, along with pressure tests and component breakdowns. Rigorous adherence to these procedures ensures optimal performance and longevity of the drive unit.

Properly requiring the correct procedures for component replacement, this manual references torque specifications for various assemblies, such as the drive shaft housing and gear housing, to ensure proper oscillation integrity and secure mounting. Technical notes and diagrams supplement the repair instructions, providing a comprehensive understanding of the system's configuration and operational parameters.

FAQ

Reference the **required** tool for drive shaft housing removal. keyboard_arrow_down

C-91-36355A1 is the specific tool required for drive shaft housing removal from the gear housing. This tool is used to press out the bearing.

What are the **essential** electrical values for the trim system? keyboard_arrow_down

12 Volts is the essential battery voltage for the trim system. The system utilizes 40 Amp fuses and 30 Amp circuit breakers for protection.

Specify the **correct** shift cable adjustment settings. keyboard_arrow_down

20-25 Ft. Lbs. (2.7-3.4mkq) is the correct torque specification for the shift cable nut and anchor stud, with specific procedures for in-line and V-8 engines detailed within the manual.

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This manual is incredibly detailed and easy to follow. The troubleshooting guide is a lifesaver! Plus, the download process was smooth, and I received the link quickly. Highly recommend!