Model:
3YM30, 3YM20, 2YM15
Model Variant:
3YM30 (3-cylinder, 1.052 L), 3YM20 (3-cylinder, 0.827 L), 2YM15 (2-cylinder, 0.570 L)
Engine Type:
Marine Diesel Engine
Production Years Covered:
YM series marine diesels; 3YM30/3YM20/2YM15 built approximately 2005-2016
Target Audience:
Boat owners, marine mechanics, and DIY technicians performing service and repair on Yanmar YM-series sailboat auxiliary engines
Market Segment:
Compact, lightweight, naturally aspirated marine diesel engines for sailboat auxiliary and small displacement powerboat use
Competitive Advantage:
High power-to-weight ratio, proven reliability, simple mechanical design, and wide parts availability support overhaul and long-term ownership
Key Features:
Water-cooled diesel, direct injection, glow plug cold starting, mechanical fuel system, 12 V electrical, optional reduction/reversing gearbox
Engine Mechanical:
Cylinder head, cylinder block, pistons, connecting rods, crankshaft, bearings, flywheel
Lubrication System:
Oil pump, oil filter, oil pressure regulation, oil galleries
Cooling System:
Seawater pump, fresh water pump, heat exchanger, thermostat, cooling circuit
Fuel System:
Fuel injection pump, injection nozzles, fuel filter, fuel feed pump, high-pressure lines
Intake and Exhaust:
Air intake, exhaust manifold, mixing elbow, silencer, turbocharger where fitted
Electrical System:
Starting motor, alternator, glow plugs, wiring harness, gauges, senders
Gearbox:
Reduction and reversing gear, clutch, gear selection, remote control
Inspection:
Scheduled inspection and component wear checks
Adjustment:
Valve clearance, injection timing, belt tension, gear linkage
Troubleshooting:
Fault diagnosis by symptom and system
Disassembly and Reassembly:
Step-by-step engine teardown and rebuild procedures
Servicing:
Engine parts servicing, cleaning, measurement, and replacement
Testing:
Compression, fuel delivery, cooling, and electrical testing
Specifications:
Tightening torques, clearances, and wear limits
Detail Level:
Highly detailed, hundreds of photos and illustrations
Illustrations:
Exploded views, cross-sections, and component diagrams
Parts Information:
Component identification and parts references for ordering
Wiring:
Electrical schematics and wiring diagrams where applicable
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:
Water-cooled, naturally aspirated 4-stroke diesel
Cylinders:
3 (3YM30, 3YM20), 2 (2YM15)
Displacement 3YM30:
1.052 L
Displacement 3YM20:
0.827 L
Displacement 2YM15:
0.570 L
Power Output 3YM30:
29.6 HP (22.1 kW) at 3600 RPM
Power Output 3YM20:
20.0 HP (14.9 kW) at 3600 RPM
Power Output 2YM15:
14.2 HP (10.6 kW) at 3600 RPM
Combustion System:
Direct injection
Cooling System:
Water cooling (seawater and fresh water circuit where fitted)
Starting:
Electric starter with glow plug start assist
Fuel System:
Mechanical direct injection
Fuel Injection Pump:
Bosch-type mechanical pump
Fuel Filter:
Replaceable cartridge with water separator
Standard Transmission:
Mechanical reduction and reversing gearbox (KM series) with direct or reduction ratio options
Optional Transmission:
Reduction ratios available; refer to manual for specific gearbox model fitted
Clutch:
Multi-disc wet clutch, mechanically actuated
Controls:
Single-lever remote control for throttle and shift
Lubrication:
Gearbox oil lubrication; refer to manual for capacity and grade
Wheelbase:
N/A - not applicable to marine engine
Length:
Refer to manual for engine dimensions
Width:
Refer to manual for engine dimensions
Height:
Refer to manual for engine dimensions
Dry Weight 3YM30:
Approximately 160 kg with gearbox
Dry Weight 3YM20:
Approximately 140 kg with gearbox
Dry Weight 2YM15:
Approximately 110 kg with gearbox
Cooling Alarm:
High coolant temperature alarm
Oil Pressure Alarm:
Low oil pressure alarm
Overheat Protection:
Thermostat and cooling system monitoring
Shielding:
Guards on rotating components where fitted
Ventilation:
Engine compartment ventilation requirements specified
Fire Safety:
Fuel system and electrical components designed to marine standards
Crash Test Information:
N/A - not applicable to marine engines
Audio System:
N/A - not applicable to marine engine
Instrumentation:
Analog gauges for RPM, coolant temperature, oil pressure, and charging
Engine Control:
Mechanical governor and shutdown system
Charging:
Alternator with internal regulator
Monitoring:
Audible and visual alarms for critical engine parameters
Table:
Refer to manual for specific intervals
Daily Checks:
Engine oil level, coolant level, fuel and water separator, belt condition, leaks
Engine Oil:
Refer to manual for specific capacity and grade
Coolant:
Refer to manual for specification
Gearbox Oil:
Refer to manual for specification
Common Wear Items:
Impeller, filters, belts, hoses, injector nozzles, glow plugs
Maintenance Notes:
Regular impeller and filter replacement essential for reliable operation
