Engine Family:
YM series marine diesel engines
Model Variants Covered:
3YM30, 3YM20, 2YM15
Engine Type:
Vertical, water-cooled, four-stroke marine diesel
Configuration:
3YM30 and 3YM20 are three-cylinder inline; 2YM15 is two-cylinder inline
Cooling System:
Freshwater (indirect) cooled with heat exchanger
Production Years Covered:
N/A - Yanmar does not publish a definitive production range; manual applies to units built under this engine series
Target Audience:
Marine technicians and DIY boat owners servicing Yanmar YM series engines
Purpose:
Provides step-by-step repair and service procedures for the 3YM30, 3YM20 and 2YM15 diesel engines
Content Scope:
Full teardown, inspection, reassembly, adjustment and troubleshooting information
Advantage:
Consolidates three related engine models into a single reference, reducing the need for multiple model-specific books
Approach:
Factory-based procedures with specification tables for wear limits and torques
Manual Type:
Repair and service manual
Delivery Method:
Instant download
Engines Covered:
Yanmar 3YM30, 3YM20 and 2YM15 marine diesel engines
Page Count:
N/A - varies with the edition supplied in the PDF file
Intended Use:
Professional workshop and owner-level maintenance and repair
Cylinder Head:
Removal, inspection, valve clearance adjustment and installation procedures
Valve Train:
Valve guides, seats, springs and rocker arm service
Cylinder Block:
Bore inspection, piston and ring service, cylinder honing
Crankshaft and Bearings:
Main and connecting rod bearing inspection and clearance checks
Flywheel and Housing:
Flywheel inspection and rear seal service
Camshaft:
Camshaft and timing gear removal, inspection and installation
Timing System:
Timing gear alignment and backlash checks
Torque Specifications:
Tightening sequences and torque values for major fasteners
Fuel Injection Pump:
Removal, timing, installation and adjustment procedures
Injectors:
Nozzle testing, cleaning and replacement
Fuel Filtering:
Filter replacement and air bleeding procedures
Governor:
Mechanical governor inspection and adjustment
Lubrication System:
Oil pump, relief valve, oil filter and pressure checks
Cooling System:
Seawater pump, freshwater pump, thermostat and heat exchanger service
Belts and Pulleys:
Drive belt inspection, tensioning and replacement
Starting System:
Starter motor removal, testing and installation
Charging System:
Alternator service and charging circuit checks
Wiring:
Harness routing, connectors and sensor diagnostics
Marine Gear and Attachments
Marine Gearbox:
Basic inspection and linkage adjustment information where applicable
Exhaust and Intake:
Manifold, mixing elbow and air intake service
Parts Information:
Component identification and part reference tables included throughout
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
3YM30 Displacement:
1.115 litres
3YM20 Displacement:
0.854 litres
2YM15 Displacement:
0.570 litres
3YM30 Rated Output:
Approximately 21 kW / 29 hp at 3600 rpm
3YM20 Rated Output:
Approximately 15 kW / 20 hp at 3600 rpm
2YM15 Rated Output:
Approximately 11 kW / 15 hp at 3600 rpm
Combustion System:
Direct injection diesel
Fuel System:
Mechanical fuel injection pump with injectors
Aspiration:
Naturally aspirated
Cooling:
Freshwater cooled with heat exchanger and seawater pump
Standard Transmission:
Yanmar marine gearbox matched to engine output
Optional Transmission:
Alternate reduction ratios available to suit vessel installation
Reduction:
N/A - exact ratio depends on the marine gear fitted
Control:
Mechanical shift lever and cable linkage
Cooling:
Marine gear oil cooler provision on applicable installations
Fluid:
Marine gear lubricant as specified by the gear manufacturer
Crash Ratings:
N/A - not applicable to a marine diesel engine
Overheat Protection:
Coolant temperature warning and alarm circuit
Oil Pressure Protection:
Low oil pressure warning and alarm circuit
Coolant Level:
Expansion tank level monitoring on installations so equipped
Shutdown Devices:
Manual stop control and optional alarm shutdown systems
Guarding:
Belt and rotating component guards on marine installations
Engine and Vessel Systems
Infotainment:
N/A - not applicable to a marine diesel engine
Instrumentation:
Tachometer, hour meter and warning lamps on the vessel panel
Starting:
Key or push-button start with preheat facility where fitted
Charging:
Belt-driven alternator for vessel electrical system
Monitoring:
Temperature, oil pressure and charging indicators
Oil and Filter Change:
Typically every 100 to 250 hours depending on duty cycle
Fuel Filter:
Replace at intervals specified in the service schedule, and after fuel contamination
Seawater Pump Impeller:
Inspect annually and replace at regular intervals or on failure
Coolant:
Check level frequently and renew at the recommended interval
Valve Clearance:
Check and adjust at the scheduled service interval
Engine Oil:
Marine diesel engine oil of the viscosity grade recommended for ambient conditions
Coolant:
Ethylene glycol based coolant mixed to the manufacturer's concentration
Common Wear Items:
Impeller, drive belts, filters, hoses, mounts and anodes
Known Issues:
Cooling system fouling, seawater pump impeller failure and exhaust mixing elbow corrosion are common on marine diesels
Manufacturer:
Yanmar Co., Ltd.
Brand Heritage:
Yanmar is a Japanese manufacturer with long experience in industrial and marine diesel engines
Model Line:
YM series is a family of compact water-cooled marine diesels used in sailboats and small craft
Evolution:
The 3YM30, 3YM20 and 2YM15 share design features across different cylinder counts and outputs
Production Location:
N/A - not specified in this manual
