All 240 pages of this Yanmar 1GM10 shop manual PDF focus on getting your diesel inboard engine running right, covering the 1GM, 2GM, 2GM20, 2GM20F, 3GM, 3GM30, 3GM30F, 3HMF, 3HM35, 3HM35F, and transmissions KM2A, KM2C, KM2P, KM3A, KM3P, KBW10D, KBW10E. Inside, you get complete wiring diagrams and high-quality exploded views to trace out any system fault. Open to the detailed troubleshooting section to rapidly diagnose charging or cooling issues, or follow the step-by-step tear-down procedures for both single and multi-cylinder blocks. Lock down the KM3P transmission mounting flange to 20-25 N-m and swap the fuel filter element exactly every 250 hours to keep the injection pump primed. Stop tearing down engines without the right numbers. Download this bookmarked file directly to your tablet, find your exact spec, and finish the rebuild.
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
Yanmar 1GM10 hard starting, loss of compression, and gray or white smoke after previously operating normally p. 68
Test the cylinder compression pressure as outlined on page 68. Verify the reading falls between 390-470 psi (2700-3300 kPa). If pressure is low, remove the exhaust elbow and inspect for internal corrosion or seawater intrusion that may have damaged the valve seats.
Manual Section: Operation, Lubrication, Maintenance and Tune-UpWeak or very low water flow at the exhaust and high overheating risk at cruising RPM p. 188
Inspect the raw-water impeller for missing vanes and check the thermostat opening temperature. Confirm the thermostat opens fully at 108° F (42° C) as specified on page 188. Replace the impeller if damaged and flush the cooling passages to remove any broken rubber debris.
Manual Section: Fuel Injection and Governor SystemsLoss of power in reverse, transmission slipping, or noisy engagement when shifting into forward gear p. 221
Measure the shifter width to ensure it is within the standard 7.80-7.85 mm (0.3071-0.3091 in.) range shown on page 221. Inspect the clutch plates and cones for wear. When reinstalling the gear assembly, torque the transmission mounting flange to 20-25 N•m (15-18 ft-lb) according to page 220.
Manual Section: Fuel Injection and Governor SystemsHeavy black smoke, bogging under load, poor throttle response, or engine dies at higher RPM p. 53
Drain the fuel tank sump to check for water or diesel bug contamination. Replace the fuel filter element, which is required every 250 hours of operation per page 53. Bleed the fuel lines completely before attempting to restart the engine to ensure proper injector operation.
Manual Section: Operation, Lubrication, Maintenance and Tune-UpFrequently Asked Questions
How do I bleed the fuel system on a Yanmar 1GM10?
Open the bleed screw on the fuel filter with the tank valve open, and work the fuel transfer pump priming lever until air-free fuel is expelled, then close it. Repeat at the fuel injection pump air-bleed screw (page 148).
Why won't my Yanmar 2GM or 3GM start?
Common causes are a low or uncharged battery, incorrect oil viscosity, corroded terminals, or loose starting-circuit connections. A defective starter, sticking brushes, or a damaged starter drive gear can also be at fault (page 46).
What causes Yanmar marine diesel overheating?
Overheating is usually a dirty cooling system, a faulty thermostat, or insufficient coolant flow. Loose belts or raw-water passages plugged with debris also cause it; clean the system and replace the thermostat as needed (page 47).
How do I align a Yanmar KM2A or KM3A marine gear?
Measure from the mounting flange mating surface to the top of each bearing race (A) and to the bottom of the bearing race bore (B), subtract A from B, then subtract 0.0–0.05 mm to get the required shim thickness, and press the outer races into the flange (page 209).
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.
Document Quality
This document is a scanned PDF with an added OCR text layer, allowing you to search and copy text throughout. The main body text is crisp and easy to read. Diagrams and illustrations are raster images from the original manual, and while generally clear, some fine details and labels may appear slightly less sharp when zoomed in. Pages are clean with consistent formatting and minimal scan artifacts. There are no notable blank or filler pages in this manual.
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