Model Series:
YM Series Marine Diesel Engines
Model Variants Covered:
2YM15, 3YM20, 3YM30
Production Years Covered:
2003-2013 (approximate; refer to engine serial number for exact build date)
Engine Type:
Vertical, water-cooled, 4-stroke marine diesel
Aspiration:
Naturally aspirated
Market Position:
Entry-level to mid-range marine diesel engines for sailboats and small motorboats
Target Audience:
Boat owners, marine mechanics, DIY repair enthusiasts
Competitive Advantage:
Lightweight, compact design; reliable and fuel-efficient; easy maintenance access
Key Features:
Freshwater cooling, direct fuel injection, electric start, optional saildrive compatibility
Engine Mechanical:
Cylinder head, block, pistons, crankshaft, bearings, valve train
Fuel System:
Fuel injection pump, injectors, fuel filter, fuel lines
Cooling System:
Seawater pump, freshwater pump, heat exchanger, thermostat, hoses
Lubrication System:
Oil pump, oil filter, oil cooler, pressure relief valve
Electrical System:
Starting motor, alternator, battery, wiring harness, sensors
Exhaust System:
Exhaust manifold, mixing elbow, exhaust hose
Transmission:
Marine gear (KM series), reduction ratios, oil specifications
Controls:
Throttle, shift, stop solenoid, instrument panel
Troubleshooting:
Diagnostic charts for common issues
Adjustments:
Valve clearance, injection timing, belt tension
Disassembly and Assembly:
Step-by-step with torque specifications
Inspection and Testing:
Compression test, oil pressure test, cooling system pressure test
Specifications:
Complete torque values, clearances, wear limits
Diagrams:
Exploded views, schematics, and flow charts
Tolerances:
Precision measurement standards for rebuilds
Component Identification:
Part names and numbers for ordering
Service Kits:
Recommended kits for periodic maintenance
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 Options:
2YM15 (2-cylinder), 3YM20 (3-cylinder), 3YM30 (3-cylinder)
Displacement:
2YM15: 0.635 L; 3YM20: 0.854 L; 3YM30: 1.115 L
Bore x Stroke:
2YM15: 70 mm x 82 mm; 3YM20: 70 mm x 74 mm; 3YM30: 78 mm x 78 mm
Configuration:
Inline, vertical
Valvetrain:
OHV, 2 valves per cylinder
Cooling:
Freshwater (closed) with seawater heat exchanger
Rated Output:
2YM15: 14 hp (10.3 kW) at 3600 rpm; 3YM20: 20 hp (14.7 kW) at 3600 rpm; 3YM30: 29 hp (21.3 kW) at 3600 rpm
Maximum Torque:
2YM15: 31 Nm at 2400 rpm; 3YM20: 44 Nm at 2400 rpm; 3YM30: 63 Nm at 2400 rpm
Combustion System:
Direct injection
Fuel Type:
Diesel (ASTM D975 No.2-D or equivalent)
Injection Pump:
Bosch-type mechanical
Fuel Filtration:
Primary and secondary filters with water separator
Standard Transmission:
Yanmar KM series mechanical marine gear
Optional Transmission:
Compatible with other marine gears (e.g., ZF, Hurth) meeting input specifications
Reduction Ratios:
Various ratios available (e.g., 2.21:1, 2.62:1, 3.22:1)
Shift Control:
Mechanical cable
Lubrication:
Same oil as engine or separate oil specified by marine gear manufacturer
Drive Type:
Direct shaft or saildrive
Cooling:
Oil cooler integral with engine cooling system
Wheelbase:
N/A - not applicable to marine engines
Length:
2YM15: 546 mm; 3YM20: 641 mm; 3YM30: 676 mm (approximate, excluding transmission)
Width:
2YM15: 457 mm; 3YM20: 457 mm; 3YM30: 476 mm
Height:
2YM15: 617 mm; 3YM20: 617 mm; 3YM30: 638 mm
Curb Weight:
2YM15: 107 kg; 3YM20: 141 kg; 3YM30: 161 kg (dry, without transmission)
Weight with Transmission:
Add approximately 15-20 kg depending on marine gear model
Cooling System:
High water temperature alarm and shutdown
Lubrication System:
Low oil pressure alarm and shutdown
Overcrank Protection:
Starting motor thermal protection
Emergency Shutdown:
Manual stop lever and electric stop solenoid
Exhaust System:
Spark arrestor and water-injection mixing elbow
Electrical:
Fuses and circuit breakers for main circuits
Standard Panel:
Tachometer, hour meter, water temperature gauge, oil pressure warning light
Optional:
Fuel gauge, voltmeter, audible alarms
Control System:
Mechanical governor and injection timing
Starting System:
12V electric start with key switch
Charging System:
12V alternator (standard output 35-55A depending on model)
Daily Checks:
Oil level, coolant level, fuel filter/water separator drain, belt tension
First 50 Hours:
Initial oil and filter change, retorque cylinder head
Every 250 Hours:
Engine oil and filter change, fuel filter change, impeller inspection
Every 500 Hours:
Valve clearance adjustment, cooling system flush, injection nozzle test
Every 1000 Hours:
Heat exchanger cleaning, water pump rebuild, injection pump calibration
Annually:
Replace impeller, inspect exhaust system, check electrical connections
Engine Oil:
API CF or higher, SAE 10W-30 or 15W-40 (depending on climate)
Coolant:
Ethylene glycol-based antifreeze mixed 50/50 with water
Fuel:
Clean diesel fuel, No.2-D
Transmission Oil:
Yanmar marine gear oil or equivalent (see marine gear manual)
Cooling System:
Seawater pump impeller wear; heat exchanger fouling in saltwater use
Fuel System:
Injection pump wear; fuel contamination causing injector clogging
Electrical:
Corrosion on connections; alternator failure
Exhaust:
Mixing elbow corrosion and blockage
Manufacturer:
Yanmar Co., Ltd.
Specialization:
Diesel engines for marine, agricultural, and industrial applications
Introduction:
YM series introduced in the early 2000s as replacement for GM series
Updates:
Minor revisions over production run; later models may have electronic governance
Discontinuation:
Replaced by common-rail YM series (e.g., 2YM15-CR) in some markets
Primary Plant:
Yanmar's Japan facilities
Reputation:
Widely regarded for reliability and longevity in marine service
Common Applications:
Used by major sailboat builders (e.g., Hunter, Catalina, Beneteau)
Certifications:
Meets EPA and EU emissions regulations for marine diesel engines
