Make:
Mercury Marine (Brunswick Corporation)
Model Variant:
55 HP Marathon outboard motor
Production Years Covered:
N/A - not specified in the supplied description
Document Type:
Workshop Service Repair Manual
Applies To:
All models within the Marathon Series
Engine Type:
Outboard motor, 2-stroke
Target Audience:
Recreational boat owners and marine service technicians
Intended Use:
Maintenance, servicing and repair at owner or workshop level
Design Focus:
Durability and ease of operation
Reputation:
Mercury engineering quality and dependable performance in its class
Application:
Recreational boating and general watercraft propulsion
Serviceability:
Engineered for straightforward maintenance and routine servicing
Powerhead:
Cylinder block, pistons, crankshaft, bearings and seals
Fuel System:
Carburetion, fuel pump, lines and tanks
Ignition System:
Flywheel, stator, trigger, coils, plugs and wiring
Charging And Starting:
Rectifier, battery circuit, starter motor and solenoid
Lower Unit:
Gearcase, driveshaft, propeller shaft, water pump and impeller
Mid Section:
Driveshaft housing, exhaust tube and mounts
Cooling System:
Impeller, thermostat, water jackets and telltale
Steering And Tilt:
Tiller or remote steering, tilt and trim components
Electrical:
Harness, switches, instruments and protective devices
Diagnostics:
Systematic troubleshooting and fault isolation charts
Adjustments:
Link and sync, throttle and shift cable adjustment, idle settings
Disassembly:
Component removal and teardown sequences for all major assemblies
Assembly:
Reassembly steps with clearances and tightening values
Repair:
Repair and rebuild procedures for powerhead, gearcase and ignition
Maintenance:
Scheduled service and seasonal preparation tasks
Specifications:
Torque values, clearances, capacities and component limits
Illustrations:
Exploded views and step diagrams for key procedures
Reference Data:
Wiring and fuel routing information for the Marathon series
Catalogue:
Part identification and location guidance within assemblies
Ordering:
Component description used for parts lookup by owners and technicians
Interchange:
N/A - specific interchange list not supplied in this edition
File Format:
PDF (searchable, bookmarked, zoomable)
Compatibility:
Windows, macOS, Linux, iOS, and Android — any device with a PDF reader
Requirements:
A PDF reader application (e.g. Adobe Acrobat Reader, free)
Searchability:
Fully text searchable for fast lookup of any topic
Print Quality:
High-resolution digital pages, printable at full clarity
Binding Type:
N/A — digital download, no physical binding
Paper Type:
N/A — digital download, no physical paper
Engine Type:
Outboard, two-stroke, water-cooled
Displacement:
N/A - not stated in the supplied description
Cylinder Count:
N/A - not stated in the supplied description
Fuel Delivery:
Carbureted
Fuel Mix:
Petrol and two-stroke oil mix per factory specification
Recommended Fuel:
N/A - exact octane rating not stated in the supplied description
Typical Application:
Recreational boats and light utility craft
Design Priority:
Dependable output with ease of operation
Gearcase Type:
Forward, neutral and reverse mechanical gearcase
Gear Engagement:
Dog clutch gear engagement via shift rod
Gear Ratio:
N/A - exact ratio varies by model year and gearcase
Alternatives:
N/A - no optional transmission offered for this model
Shift Control:
Tiller or remote shift control depending on boat rigging
Lubrication:
Gearcase oil bath
Propeller:
Shaft drive with splined propeller hub
Shaft Lengths:
N/A - offered in multiple shaft lengths by application
Weight Class:
N/A - depends on shaft length and configuration
Mounting:
Transom mount with clamp or bolt bracket
Curb Weight:
N/A - not stated in the supplied description
Gearcase Oil:
N/A - capacity depends on gearcase variant
Crash Test Ratings:
N/A - not applicable to outboard motors
Certification:
Built to Mercury marine engine standards of the era
Kill Switch:
Emergency lanyard stop circuit
Overheat Protection:
Cooling system telltale and temperature monitoring
Cowling:
Removable cover shielding ignition and rotating components
Water Pump:
Tell-tale indicator shows coolant flow to alert on pump failure
Ignition:
CD ignition with stator and trigger assembly
Charging:
Battery charging circuit on electric-start models
Starting:
Manual recoil and/or electric start depending on variant
Audio System:
N/A - not fitted to outboard motors
Trim And Tilt:
Power or manual tilt and trim depending on configuration
Instrumentation:
Tachometer, trim gauge and warning horn wiring covered in the manual
Gearcase Oil:
Every 100 hours or annually, whichever comes first
Water Pump Impeller:
Replace at scheduled intervals or on pressure loss
Spark Plugs:
Inspect and replace at scheduled service intervals
Fuel Filter:
Replace at scheduled intervals or on contamination
Gearcase Lubricant:
Marine high-viscosity gear lubricant per factory recommendation
Fuel Mixture:
Two-stroke fuel and oil mix per factory ratio sticker
Grease Points:
Water-resistant marine grease on pivot and steering points
Known Issues And Wear Items
Water Pump Impeller:
Common wear item; hardened or torn vanes reduce cooling
Fuel System:
Carburetor varnish and fuel line degradation after long storage
Ignition:
Stator and coil faults causing weak or intermittent spark
Corrosion:
Anodes and fasteners require inspection in saltwater use
Manufacturer:
Mercury Marine, a Brunswick Corporation brand
Mariner Line:
Mariner branded engines shared Mercury engineering and platforms
Marathon Series:
Positioned as a durable, easy-to-operate outboard range
Production Years:
N/A - exact years not specified in the supplied description
Assembly:
N/A - specific plant not stated for this model
