1998 Mercury Mariner 20 JET, 20, 25, 25 MARATHON und 25 SEAPRO Outboard Motor Service Manual

Technical reference spanning Mercury Mariner 20 JET, 20, 25, 25 MARATHON, and 25 SEAPRO models, covering engine specifications, maintenance, and electrical systems. Includes part numbers like 92-78376A6.

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Document Details

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Document Number / Seller:
27174 / Lisa Owens
File Size:
11.76 MB
File Type:
PDF
Language:
English
Printable:
Yes
Category:
Outboard Motor
Last updated / verified
Apr 24, 2025

Models Covered & Key Technical Specifications

1998 Mercury Mariner 20 JET, 20, 25, 25 MARATHON und 25 SEAPRO Outboard Motor Service Manual (20HP/25 HP) This manual provides comprehensive coverage for your Mercury Mariner outboard motor.

  • Technical Specifications: Detailed breakdown of engine components and their capabilities.
  • Maintenance Procedures: Guided steps for routine upkeep and preventative care.
  • Electrical Systems: Diagrams and explanations for ignition and charging systems.
  • Fuel System: Information on carburetor adjustments and fuel delivery.
  • Powerhead Reassembly: Step-by-step instructions for internal engine components.
  • Troubleshooting Guide: Solutions for common issues and diagnostic procedures.

Professional Workshop Service Manual & Technical Specifications

Thorough Specification Reference Manual: Outboard Motor Mercury 20 JET, 20, 25, 25 MARATHON und 25 SEAPRO HP Outboard - Service & Repair Manual (1998 Models) Service-Portfolio

Model-Portfolio: Mercury 20 JET / 20 / 25 / 25 MARATHON / 25 SEAPRO // Service-Level: Outboard Motor / Engine Logic // Model-Portfolio: 1998 Outboard Motor Repair Documentation.

Metric Diagnostic-Logic Calibration-Standards
Horsepower 20 (14.9) - 25 (18.7) HP 20-25 HP Range Comprehensive Performance Metrics
Outboard Weight 114 lbs - 124 lbs Specified by shaft length Detailed Weight Specifications
Cylinder Block Two Cycle, 24.4 cu. in. (400 cc) Standard Displacement Engine Block Configuration Details
Crankshaft 1.251 in. - 1.196 in. Journals Precision Machined Components Crankshaft Assembly Specifications
Ignition System Capacitor Discharge Ignition Spark Plug NGK BP8H-N-10 Ignition Timing Data

OEM specifications cover engine power, displacement, and component dimensions. This manual provides detailed diagrams and procedural guides for all aspects of outboard motor service and repair, from engine disassembly to electrical system maintenance. It covers all major systems, including fuel delivery, ignition, starting, and charging, with specific attention to the powerhead and its internal components. Troubleshooting guidance is also provided for common issues encountered with these Mercury Mariner models.

Torque specifications for critical components like the crankshaft and cylinder block are documented to ensure proper assembly and pressure slip prevention. The manual details procedures for maintenance, component inspection, and assembly, aiming to ensure the longevity and optimal performance of the outboard motor.

System Operations: Covers ignition system components, carburetor adjustments, and fuel pump service. Details maintenance schedules and procedures for battery charging and starting systems, as well as timing and synchronizing adjustments. Includes troubleshooting tips for common engine problems like rough idle or starting difficulties. The manual addresses specific components like the stator, flywheel, and starter motor.

FAQ

What **calibrated** values are specified for the ignition system architecture? keyboard_arrow_down

4° ± 2° B.T.D.C is the specified idle timing, not adjustable, and 25° ± 1 @5500 RPM is the maximum BTDC specified for the ignition system architecture.

Assess the **applicable** tool requirements for starter motor assembly. keyboard_arrow_down

A Strap Wrench (91-24937A1) is required for holding the armature while removing the locknut, and a Piston Pin Tool (91-76160A2) is applicable for piston pin removal during piston and rod disassembly.

What **exact** electrical values are documented for the stator windings? keyboard_arrow_down

For the BLACK stator, the high-speed winding resistance is 2800 – 3400 Ω (RED – BLUE), and the low-speed winding resistance is 100 – 180 Ω (RED – BLK).

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Reviews (3)

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Rated 4 out of 5 stars
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This manual is a must-have for anyone working on a 1998 Mercury or Mariner outboard motor. The detailed instructions and troubleshooting tips have saved me a lot of time and effort. The download process was smooth, and I received the link quickly after purchase!
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I found this service manual incredibly helpful. The sections on carburetor servicing and adjustments were particularly well laid out. I had a quick question and reached out via email; their support team responded in no time! Definitely worth the investment.