Part of the Yanmar Repair Manuals.
Before you condemn a tired 1GM10 head, take a compression reading and compare it against the figure this shop manual gives: 390 to 470 psi. That is the kind of number that stalls a rebuild when you do not have it, and this book puts it in the Quick Reference Data along with tune-up specs, oil capacities, and general torque values.
The manual covers the Yanmar 1GM, 1GM10, 2GM, 2GM20, 2GM20F, 3GM, 3GM30, 3GM30F, 3HMF, 3HM35, and 3HM35F marine inboard diesels, plus the KM2A, KM2C, KM2P, KM3A, KM3P, KBW10D, and KBW10E marine gears. Its 240 pages run from troubleshooting and maintenance through full single-cylinder and multicylinder teardown chapters to the fuel injection and governor systems.
It downloads as a 64 MB English PDF. Print the torque tables and let them get dirty at the stand; the file stays clean.
Complete the set for your GM/HM Series & KM Gears
What's Inside This Yanmar GM/HM Series & KM Gears Manual
| System | Pages | Key Topics |
|---|---|---|
| Quick Reference Data | 3-7 | Tune-Up Specifications, Approximate Engine Oil Capacities, Freshwater (Closed) Cooling System Capacity, Engine Models, General Torque Specifications |
| General Information | 8-31 | Manual Organization, Notes, Cautions and Warnings, Safety First, Service Hints, Parts Replacement, Torque Specifications, Fasteners |
| Troubleshooting | 32-47 | Starting System, Charging System, Charging System Tests, Fuel System, Cooling System, Engine Exhaust Smoke, Engine Noises, Engine Troubleshooting |
| Operation, Lubrication, Maintenance and Tune-Up | 48-68 | Fuel Requirements, Preoperational Checks, Starting Checklist, Stopping the Engine, Emergency Engine Stopping, Post-Operational Checks, Engine Maintenance and Lubrication |
| Lay-Up and Fitting Out | 69-73 | Lay-Up, Cooling System Draining, Fitting Out |
| Single-Cylinder Engines | 74-104 | Diesel Engine Fundamentals, Engine Serial Number and Code, Replacement Parts, Engine Removal Precautions, Valve Cover, Breather Assembly, Decompression Mechanism, Cylinder Head |
| Multicylinder Engines | 105-143 | Engine Serial Number and Code, Replacement Parts, Engine, Valve Cover, Breather Assembly, Decompression Mechanism, Exhaust Manifold, Cylinder Head |
| Fuel Injection System | 145-149 | Fuel Tank, Fuel Valve, Fuel Feed Pump, Fuel Return Hose, Fuel Filter, Fuel Injector, High Pressure Fuel Pipe |
| Fuel Injection Timing | 150-154 | Injection Timing Shims, Plunger Roller, Fuel Injection Cam, Spill Pipe, Retainer Plate, O-Ring, Gasket |
| Fuel Injection Pump | 155-157 | Fuel Transfer Pump, Fuel Lines |
| Governor System | 158-240 | Governor Assembly, Governor Sleeve, Crankshaft |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| 2GM, 2GM20, 3GM, 3GM30, 3HM, 3HM35 | ||
| Cylinder head torque | 120 N•m (88 ft-lb) | p. 143 |
| KM2A, KM2C, KM2P, KM3A, KM3P | ||
| Transmission mounting flange torque | 20-25 N•m (15-18 ft-lb) | p. 220 |
| All Models | ||
| Fuel filter element replacement interval | every 250 hours of operation | p. 53 |
| Compression Pressure | 390-470 psi (2700-3300 kPa) | p. 68 |
| 1GM, 1GM10 | ||
| Engine Oil Capacity | 1.4 qt (1.3 L) | p. 6 |
| Battery Voltage | 12 V | p. 204 |
| 2GM20F | ||
| Freshwater Cooling System Capacity | 2.9 L (0.77 gal.) | p. 6 |
| All engines | ||
| Thermostat Opening Temperature | 108° F (42° C) | p. 188 |
| KM Series | ||
| Transmission Mounting Flange Torque | 20-25 N•m (15-18 ft-lb) | p. 220 |
| KM2A, KM2C, KM3A | ||
| Shifter Width (Standard) | 7.80-7.85 mm (0.3071-0.3091 in.) | p. 221 |
Yanmar GM/HM Series & KM Gears Common Problems This Manual Covers
Engine cranks but will not start
A GM or HM series diesel that spins over and never fires usually comes down to fuel delivery, compression, or the stop mechanism, and guessing wrong wastes a day. The Troubleshooting chapter walks the starting system, fuel system, and engine troubleshooting charts in order so you eliminate causes instead of parts.
Manual Section: Troubleshooting p. 32Corroded exhaust elbow choking the engine
Seawater scale slowly closes the exhaust path on these engines, and a blocked or leaking elbow can push water back toward the valves and rob compression. The Multicylinder Engines chapter covers exhaust manifold removal and inspection along with the cylinder head work that follows if water got in.
Manual Section: Multicylinder Engines p. 105Weak seawater discharge and overheating
A thin stream at the exhaust outlet means the raw water side is failing, and running on like that cooks the engine. The maintenance chapter covers cooling system checks and service as part of the regular lubrication and tune-up routine, so you catch a dying impeller before it sheds vanes into the plumbing.
Manual Section: Operation, Lubrication, Maintenance and Tune-Up p. 48Black smoke and bogging under load
Heavy smoke and an engine that dies when you ask for power point at the injection side: contaminated fuel, tired injectors, or timing that has drifted. The Fuel Injection and Governor Systems chapter covers injection timing, the injection pump, and governor service in detail.
Manual Section: Fuel Injection and Governor Systems p. 144Low compression after long storage
An engine that sat unprotected often wakes up with sticking or corroded valves and soft compression. The Single-Cylinder Engines chapter takes the 1GM and 1GM10 through cylinder head removal, valve and valve seat work, and the decompression mechanism, with the piston and connecting rod procedures behind them if the bores need attention.
Manual Section: Single-Cylinder Engines p. 74Winterizing damage from a skipped lay-up
Freezing water left in the cooling system, or fuel and cylinders left unpreserved, causes more damage over a winter than a season of running. The Lay-Up and Fitting Out chapter gives the storage procedure, cooling system draining, and the fitting out steps for spring.
Manual Section: Lay-Up and Fitting Out p. 69Frequently Asked Questions
Which Yanmar engines does this shop manual cover?
The 1GM, 1GM10, 2GM, 2GM20, 2GM20F, 3GM, 3GM30, 3GM30F, 3HMF, 3HM35, and 3HM35F marine inboard diesels, along with the KM2A, KM2C, KM2P, KM3A, KM3P, KBW10D, and KBW10E marine gears.
Does it cover the fuel injection pump and governor?
Yes. The Fuel Injection and Governor Systems chapter, the longest in the book, covers the fuel injection system, injection timing, the injection pump, and the governor. p. 144
Where do I find torque specs and tune-up values?
The Quick Reference Data section at the front collects tune-up specifications, engine oil capacities, freshwater cooling capacities, and general torque specifications, so the numbers you need before reassembly sit in one place instead of scattered through the procedures. p. 3
Does it explain winter storage for these engines?
Yes. The Lay-Up and Fitting Out chapter covers the lay-up procedure, draining the cooling system, and the fitting out checks before the engine goes back into service. p. 69
Is this a digital download?
Yes. You get the full 240-page Shop Manual as a searchable PDF, ready to download the moment checkout completes. Open it on a computer, tablet, or phone.
Can I print this manual?
Yes. The PDF is DRM-free, so you can print any page or section you need to take out to the shop. Standard letter or A4 paper works.
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