Part of the Yanmar Repair Manuals.
Setting valve lash on a 1GM10 or timing the injection pump on a 3HM35 stalls fast without the factory figures, and guessing at a head bolt sequence is how a rebuild goes wrong. This Yanmar service manual (publication 0000 A0A1361) puts the same 474 pages Yanmar's own technicians work from on your bench, covering the GM series marine diesels 1GM10(C), 2GM20(F)(C), 3GM30(F)(C), and 3HM35(F)(C) in both sea-water and fresh-water cooled versions.
Inside are teardown and reassembly procedures for the basic engine, fuel injection system, governor, lubrication system, both cooling systems, and the reduction and reversing gear, plus specifications, cross-sections, and piping diagrams. Chapter 9 even walks through converting a sea-water cooled engine to fresh water cooling.
It downloads as a bookmarked PDF, so the specs travel with you: a laptop at the bench, a phone in the engine bay, or printed pages clipped beside a torn-down block.
What's Inside This Yanmar GM/HM Series Manual
| System | Pages | Key Topics |
|---|---|---|
| History of Revision | 3 | Safe Servicing Information, Engine Specifications, Manual Content Updates |
| A. Engine Model Name | 9 | |
| B. Engine Model Name Plate and Clutch Model Name Plate | 10-11 | Item Descriptions on Model Name Plates, Information to Be Forwarded to Us, Engine Model Name Plate Location, Clutch Model Name Plate Location |
| Cylinder Number | 12 | Cylinder Numbering Sequence |
| For Safety | 13-18 | 1. for Safe Servicing, Precaution for Safe Servicing |
| General | 19-47 | Specifications, Principal Construction, Performance Curves, Engine Cross-Sections, Dimensions, Piping Diagrams |
| Basic Engine | 48-111 | Cylinder Block, Cylinder Head, Piston, Connecting Rod, Crankshaft, Flywheel and Housing, Camshaft, Timing Gear |
| Fuel System | 112-146 | Fuel Injection System, Injection Pump, Injection Nozzle, Fuel Filter, Fuel Feed Pump, Fuel Tank(Option) |
| Governor | 147-160 | Injection Limiter, No-Load Maximum Speed Limiter, Idling Adjuster, Engine Stop Lever |
| Intake and Exhaust System | 161-168 | Intake Silencer, Exhaust System, Breather |
| Lubrication System | 169-183 | Oil Pump, Oil Filter, Oil Pressure Regulator Valve, Oil Pressure Measurement |
| Direct Sea-Water Cooling System | 184-201 | Cooling System, Water Pump, Thermostat, Anticorrosion Zink, Kingston Cock(Optional), Bilge Pump and Bilge Strainer(Optional) |
| Fresh Water Cooling System | 202-220 | Cooling System, Sea Water Pump, Fresh Water Pump, Heat Exchanger, Filler Cap and Subtank, Thermostat, Cooling Water Temperature Switch, Precautions |
| Modifying the Cooling System | 221-233 | General, Disassembly of Sea Water-Cooled Engine, Assembling Modified Parts to the Fresh Water -Cooled Engine, Cautions When the Engine Is Installed Inboard |
| Reduction and Reversing Gear | 234-333 | [A] for Engine Models 1GM10.2GM20 and 3GM30 (Construction, Shifting Device, Servicing, Disassembly, Reassembly) |
| Remote Control System | 334-341 | Clutch and Speed Regulator Remote Control, Engine Stop Remote Control |
| Electrical System | 342-387 | Battery, Starter Motor, Alternator Standard 12V/55A, Alternator Option 12V/35A, Instrument Panel, Tachometer |
| Operating Instructions | 388-403 | Fuel Oil and Lubricating Oil, Engine Operating Instructions, Troubleshooting and Repair |
| Disassembly and Reassembly (Direct Sea-Water Cooling Engine) | 404-447 | Disassembly and Reassembly Precautions, Disassembly and Reassembly Tools, Disassembly, Reassembly |
| Disassembly and Reassembly (Fresh Water Cooling Engine) | 448-472 | Disassembly of Fresh Water-Cooled Engine, Reassembly of Fresh Water-Cooled Engine, Tightening Torque, Packing Supplement and Adhesive Application Point |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| 1GM10(C), 2GM20(F)(C), 3GM30(F)(C) | ||
| Idling Speed (High) (1GM10(C), 2GM20(F)(C), 3GM30(F)(C)) | 3825 ± 25 min⁻¹ | p. 20 |
| Compression Ratio (1GM10(C), 2GM20(F)(C), 3GM30(F)(C)) | 23.0 | p. 20 |
| 3HM35(F)(C) | ||
| Idling Speed (High), 3HM35(F)(C) | 3600 ± 25 min⁻¹ | p. 20 |
| Compression Ratio, 3HM35(F)(C) | 24.8 | p. 20 |
| 1GM10(C) | ||
| Fuel Injection Pressure, 1GM10(C) | 170 kgf/cm² (2418 lb/in.²) | p. 114 |
| 2GM20(F)(C), 3GM30(F)(C), 3HM35(F)(C) | ||
| Fuel Injection Pressure (2GM20(F)(C), 3GM30(F)(C), 3HM35(F)(C)) | 160 kgf/cm² (2276 lb/in.²) | p. 114 |
Yanmar GM/HM Series Common Problems This Manual Covers
Cranks but will not fire
A GM series diesel that spins over without lighting usually has air in the fuel lines, a clogged filter, or a tired injection pump. The fuel system chapter covers the injection pump, injection nozzles, fuel filter, and feed pump so you can test each stage instead of swapping parts.
Manual Section: Chapter 3 Fuel System p. 112Overheating on sea-water cooled engines
Rising temperature under load on a raw-water cooled engine points to a worn water pump, a stuck thermostat, or neglected anticorrosion zincs. This chapter covers the water pump, thermostat, and zinc service needed to restore flow before heat gets to the cylinder head.
Manual Section: Chapter 7 Direct Sea-Water Cooling System p. 184Temperature creep on fresh-water cooled models
On the (F) versions, slow overheating usually traces to the heat exchanger, the sea water pump feeding it, or a lazy fresh water pump. The fresh water cooling chapter covers all three, plus the filler cap, subtank, thermostat, and temperature switch.
Manual Section: Chapter 8 Fresh Water Cooling System p. 202Low oil pressure warning
An oil pressure alarm at idle can mean a worn oil pump, a sticking pressure regulator valve, or bearings on their way out. This chapter gives the oil pump and regulator valve procedures along with an oil pressure measurement method, so you diagnose before you split the block.
Manual Section: Chapter 6 Lubrication System p. 169Hunting or surging idle
An idle that swings up and down points to the governor or its adjusters rather than the pump itself. The governor chapter covers the governor, injection limiter, no-load maximum speed limiter, and idling adjuster so you can set it right instead of chasing it.
Manual Section: Chapter 4 Governor p. 147Weak compression and blowby
Hard starting when cold, breather smoke, and oil use come down to rings, valves, and the head. The basic engine chapter covers the cylinder block, cylinder head, pistons, connecting rods, and crankshaft, which is where you find the measuring and reassembly work for a proper rebuild.
Manual Section: Chapter 2 Basic Engine p. 48Reversing gear slips or shifts hard
A clutch that slips under load or balks going into reverse is a gearbox job, not an engine job. The reduction and reversing gear chapter covers construction, the shifting device, servicing, disassembly, and reassembly.
Manual Section: Chapter 10 Reduction and Reversing Gear p. 234Frequently Asked Questions
Which Yanmar engines does this service manual cover?
The GM series marine diesels: 1GM10(C), 2GM20(F)(C), 3GM30(F)(C), and 3HM35(F)(C), in both sea-water cooled and fresh-water cooled (F) versions. It is the Yanmar factory service manual, publication 0000 A0A1361.
Does it cover injection pump and injector service?
Yes. The Chapter 3 Fuel System section covers the fuel injection system, injection pump, injection nozzles, fuel filter, and fuel feed pump, so you can work through a no-start or rough-running fault stage by stage. p. 112
Does it cover both raw-water and fresh-water cooling?
Yes. Chapter 7 covers the direct sea-water cooling system, including the water pump, thermostat, and anticorrosion zincs, and Chapter 8 covers the fresh water system with its sea water pump, fresh water pump, and heat exchanger. Chapter 9 also explains modifying a sea-water cooled engine to fresh water cooling. p. 184
Is the marine gearbox included?
Yes. The Chapter 10 Reduction and Reversing Gear section covers construction, the shifting device, servicing, disassembly, and reassembly, and Chapter 11 covers the remote control system for the clutch, speed regulator, and engine stop. p. 234
How quickly can I access this manual after buying?
Instant PDF download. You get the full 474-page searchable Service Manual immediately after payment. Open it on your laptop, tablet, or phone right in the shop.
Is this Yanmar 1GM10(C) & variants Service Manual printable?
Yes. The PDF has no DRM restrictions, so print any page or section you need for your shop. Works with any standard printer.
Does this Service Manual have electrical diagrams?
Yes. The Electrical System section at p342-387 carries the electrical wiring diagrams for this machine.
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