Model Series:
YM Series Marine Diesel Engines
Model Variants Covered:
3YM30, 3YM20, 2YM15
Engine Type:
Vertical, water-cooled, 4-stroke marine diesel
Production Era:
YM series introduced early 2000s; manual covers the listed model run
Manual Application:
Sailboat and small craft auxiliary propulsion and generator use
Target Audience:
Boat owners, marine technicians, and DIY engine maintainers
Intended Use:
Auxiliary power for sailboats and small displacement craft
Compact Design:
Two- and three-cylinder layout suited to tight engine compartments
Cooling:
Freshwater (closed) cooling with heat exchanger on most installations
Serviceability:
Accessible service points for routine maintenance
Fuel:
Diesel, mechanically governed for reliable marine operation
Manual Type:
Service and repair manual for marine diesel engines
Delivery:
Instant download
Page Count:
N/A - varies by edition; refer to the product page listing
Engines Covered:
Yanmar 3YM30, 3YM20, 2YM15
Content Scope:
Specifications, maintenance, disassembly, inspection, reassembly, and adjustment procedures
Engine Mechanical:
Cylinder head, block, pistons, connecting rods, crankshaft, bearings
Valve Train:
Valves, springs, guides, seats, rocker assembly, pushrods
Lubrication System:
Oil pump, oil filter, oil galleries, pressure relief
Cooling System:
Raw water pump, heat exchanger, thermostat, freshwater pump, hoses
Fuel System:
Fuel lift pump, fuel filter, injection pump, injectors, fuel lines
Governor:
Mechanical governor adjustment and operation
Starting System:
Starter motor, starter relay, key switch circuit
Charging System:
Alternator, regulator, battery charging circuit, warning lamp
Electrical System:
Wiring, sensors, senders, alarms, and instrument panel
Exhaust System:
Exhaust manifold, mixing elbow, and cooling water injection
Marine Gear:
Transmission mounting and coupling to engine (as equipped)
Specifications:
Torque values, clearances, wear limits, and service capacities
Maintenance:
Scheduled service and adjustment procedures
Disassembly:
Step-by-step teardown procedures
Inspection:
Component inspection and measurement criteria
Reassembly:
Assembly procedures with torque sequences
Troubleshooting:
Diagnostic charts for common faults
Level:
Component-level service and overhaul detail
Illustrations:
Diagrams and exploded views supporting the procedures
Parts Information:
Component identification and reference to part numbers where listed
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:
3-cylinder, approx. 29 hp class marine diesel
3YM20:
3-cylinder, approx. 20 hp class marine diesel
2YM15:
2-cylinder, approx. 14 hp class marine diesel
Combustion Cycle:
4-stroke diesel
Cooling:
Freshwater cooled with heat exchanger
Aspiration:
Naturally aspirated
Valve Arrangement:
OHV, pushrod-operated
Fuel System:
Mechanical indirect diesel injection with distributor-type pump
Rated Output:
Refer to the engine nameplate and manual specification tables for the exact rating
Rated Speed:
Marine continuous rating; confirm from the manual specification table
Type:
Mechanical marine reduction gear (as equipped)
Engine Coupling:
Flywheel housing and damper plate interface
Options:
Various reduction ratios available; confirm the gear model fitted to the engine
Shift Control:
Single-lever mechanical shift and throttle control
Output:
Propeller shaft coupling at the marine gear output flange
Model:
3YM30 / 3YM20 / 2YM15
Overall Dimensions:
Refer to the manual dimension drawing for the exact figures
Wheelbase:
N/A - not applicable to a marine engine
Dry Weight:
Refer to the manual specification table for the exact figure per model
Curb Weight:
N/A - marine engine, dry weight is the published reference
Engine Protection:
Low oil pressure and high coolant temperature warning alarms
Cooling:
Raw water flow and overheat monitoring
Shutdown Equipment:
Optional alarm and shutdown systems available
Crash Test Ratings:
N/A - not applicable to a marine engine
Marine Standards:
Built for marine auxiliary propulsion use per Yanmar marine engine practice
Panel:
Marine instrument panel with gauges and warning lamps
Monitoring:
Oil pressure, coolant temperature, and charge warning indication
Governor:
Mechanical speed control for steady propeller loading
Starting:
Electric key-start with standard marine wiring harness
Break-In Service:
Initial service after the first operating hours; follow the manual schedule
Daily Checks:
Oil level, coolant level, raw water flow, fuel and oil leaks
Periodic Service:
Oil and filter, fuel filter, raw water impeller, and zinc anodes at the scheduled intervals
Engine Oil:
Marine diesel engine oil of the grade specified in the manual
Coolant:
Freshwater coolant/antifreeze mix as specified for marine engines
Fuel:
Clean diesel fuel; keep water and contaminants out of the system
Common Items:
Raw water impeller, fuel and oil filters, anodes, belts, and hoses
Area to Inspect:
Exhaust mixing elbow and heat exchanger for corrosion and blockage
Background:
Established manufacturer of diesel engines for marine and industrial use
Series:
YM series marine diesel engines replaced earlier Yanmar marine engine families
Product Family:
2YM15, 3YM20, and 3YM30 share design features across the range
Production Location:
Yanmar marine engine manufacturing
Application:
Sailboat and small craft auxiliary power worldwide
