Part of the Yanmar Repair Manuals.
Set the cylinder head back on a 2QM20 without the torque figure in front of you and you are gambling a casting that costs many times what this manual does. Yanmar's factory service manual F027A2223 covers the 2QM20, 2QM20H, 2QM20Y and 2QM20F twins and the 3QM30, 3QM30H, 3QM30Y and 3QM30F triples, 349 pages running from the cylinder block out to the reduction and reversing gear.
The numbers a rebuild lives on are here: cylinder head nuts at 18 plus or minus 1.5 kg·m, connecting rod bolts at 5.5 to 6.0 kg·m, injector pop pressure of 160 kg/cm², and thermostat opening temperatures for both the seawater cooled and freshwater cooled versions. Fuel system, governor, lubrication, electrical and full disassembly procedures round it out.
As a PDF it travels: on the bench beside the block, in a locker aboard, or on the phone in your pocket.
What's Inside This Yanmar 2QM20 / 3QM30 Series Manual
| System | Pages | Key Topics |
|---|---|---|
| General | 4-43 | Exterior Views, Specifications, Principal Construction, Performance Curves, Engine Cross-Section, Dimensions, System Diagrams |
| Basic Engine | 44-84 | Cylinder Block, Cylinder Liner, Cylinder Head, Piston, Connecting Rod, Crankshaft, Camshaft, Timing Gear |
| Fuel System | 85-106 | Injection Pump, Injection Valve, Fuel Filter, Fuel Feed Pump, Fuel Tank (Option) |
| Governor | 107-115 | Injection Limiter, No-Load Maximum Speed Limiter, Idling Adjuster |
| Intake and Exhaust System | 116-122 | Intake Silencer, Exhaust System, Breather Pipe, Intake Manifold [3QM30(H)] |
| Lubrication System | 123-134 | Oil Pump, Oil Filter, Oil Pressure Regulator Valve, Oil Pressure Measurement |
| Cooling System | 135-162 | Sea Water Cooling (Cooling System, Water Pump and Bilge Pump, Thermostat, Anticorrosion Zinc, Kingston Cock, Bilge Strainer) |
| Chain-Overdrive Hand-Operated System | 163-166 | - |
| Reduction and Reversing Gear | 167-223 | For Model 2QM20, 3QM30 (Construction, Installation and Operation, Handling the Reduction and Reversing Gears, Servicing, Disassembly, Reassembly) |
| Remote Control System | 224-232 | Clutch and Speed Regulator Remote Control, Decompression Remote Control, Engine Stop Remote Control |
| Electrical System | 233-262 | Composition, Battery, Starter Motor, Alternator, Alarm Circuit |
| Installation and Fitting | 263-291 | Propeller Selection, Engine Installation, Stern Equipment, Interior Piping and Wiring, Front Power Take-Off |
| Operating Instructions | 292-307 | Fuel Oil and Lubricating Oil, Engine Operating Instructions, Troubleshooting and Repair |
| Disassembly and Reassembly | 308-341 | Disassembly and Reassembly Precautions, Disassembly and Reassembly Tools, Other, Disassembly, Reassembly, Tightening Torque, Packing Supplement and Adhesives |
| Inspection and Servicing | 342-348 | Periodic Inspection and Servicing |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Delivery valve holder tightening torque | 4 ~ 4.5 kg·m (29 ~ 32.6 lb·ft) | p. 95 |
| Injection pressure | 160 kg/cm² (2,270 lb/in.²) | p. 102 |
| Thermostat opening temperature (sea water cooling) | 42°C | p. 143 |
| Thermostat full open temperature (sea water cooling) | 52°C | p. 143 |
| Oil filter replacement period | Every 300 hours of engine operation | p. 132 |
| Fuel filter cleaning period | Every 50 hours | p. 104 |
| Fuel filter element replacement period | Every 100 hours | p. 104 |
| Cylinder head packing agent and adhesive | Three Bond No. 4, Three Bond No. 50, Screw Lock Super 203M | p. 341 |
| Cylinder block packing agent and adhesive | Three Bond 388-005 | p. 341 |
| Corrective action for thermostat faulty (cooling water temperature high) | Replace thermostat | p. 307 |
| Bore × Stroke | 88 × 90 mm | p. 9 |
| Displacement | 1088 cc | p. 9 |
Yanmar 2QM20 / 3QM30 Series Common Problems This Manual Covers
Cranks but will not fire
Long cranking with no start on these engines usually traces to contaminated fuel, a clogged filter or air in the lines. The Fuel System chapter covers the injection pump, injection valve, feed pump and filter, with a cleaning interval of every 50 hours and element replacement every 100 hours.
Manual Section: Chapter 3 Fuel System p. 85Overheating with water still flowing
Running hot despite an apparently healthy raw water flow points to a stuck thermostat, a tired pump or spent anticorrosion zinc. The Cooling System chapter covers both seawater and freshwater circuits, including thermostat test temperatures and the 500 hour zinc replacement interval.
Manual Section: Chapter 7 Cooling System p. 135Low or falling oil pressure
A sagging gauge means checking the oil filter, due every 300 hours, and the oil pressure regulator valve before condemning the pump. The Lubrication System chapter walks through the pump, filter, regulator valve and the oil pressure measurement procedure itself.
Manual Section: Chapter 6 Lubrication System p. 123Surging or hunting at idle
An engine that will not hold a steady idle needs the governor looked at, not just the throttle linkage. This chapter covers the governor itself plus the injection limiter, no-load maximum speed limiter and idling adjuster.
Manual Section: Chapter 4 Governor p. 107Blue smoke and rising oil consumption
Oil going out the exhaust on a high hour QM usually means worn rings or valve guides. The Basic Engine chapter covers the cylinder liner, piston, connecting rod, crankshaft and cylinder head, the measuring work that tells you whether a rering or a full rebuild is due.
Manual Section: Chapter 2 Basic Engine p. 44Reversing gear slips or shifts hard
A gearbox that hesitates going into gear or slips under load is a teardown you do not want to guess through. The Reduction and Reversing Gear chapter gives construction, servicing, disassembly and reassembly for the 2QM20 and 3QM30 units.
Manual Section: Chapter 9 Reduction and Reversing Gear p. 167No charge or false alarm warnings
A dead battery or an alarm that cries wolf sends you to the Electrical System chapter, which covers the battery, starter motor, alternator and alarm circuit, including the 35A/5000 rpm standard alternator output figure to test against.
Manual Section: Chapter 11 Electrical System p. 233Frequently Asked Questions
Which engines does this manual cover?
The Yanmar 2QM20, 2QM20H, 2QM20Y and 2QM20F, and the 3QM30, 3QM30H, 3QM30Y and 3QM30F marine diesels, in both seawater cooled and freshwater cooled versions. It is the factory service manual, publication F027A2223, 349 pages in English.
Does it cover both seawater and freshwater cooling systems?
Yes. The Cooling System chapter has separate sections for each: seawater cooling with the water pump, Kingston cock and anticorrosion zinc, and freshwater cooling with its own pump, tank and thermostat. Thermostat opening temperatures are given for both, 42°C seawater and 71°C freshwater. p. 135
Are torque specifications included for reassembly?
Yes. The Disassembly and Reassembly chapter includes a tightening torque table, with cylinder head nuts at 18 plus or minus 1.5 kg·m and connecting rod bolts at 5.5 to 6.0 kg·m, plus a chart of the sealants and adhesives Yanmar specifies for each joint. p. 308
Does the manual give maintenance intervals?
Yes. The Inspection and Servicing chapter lays out periodic inspection and servicing, and the system chapters give specific intervals such as fuel filter cleaning every 50 hours, element replacement every 100 hours, oil filter replacement every 300 hours and anticorrosion zinc every 500 hours. p. 342
How will I receive this Service Manual?
Immediate download of the complete 349-page searchable Service Manual (19 MB). Access it on any device, from a laptop at your desk to a phone in the field.
Is this manual print-friendly?
No restrictions at all. Print individual pages, full chapters, or the entire manual. The PDF is completely unlocked.
Can I trace circuits with this Yanmar 2QM20(H) manual?
Yes, this Yanmar 2QM20(H), 3QM30(H), 2QM20, 2QM20Y, 2QM20F, 3QM30, 3QM30Y, 3QM30F Service Manual includes complete electrical wiring diagrams, wire routing, and connector pinouts.
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