Part of the Yanmar Operator Manuals.
Bleed the fuel system in the wrong order on a 2GM20F and you can crank the battery flat without a single fire. This Yanmar operator manual, publication 128270-4E, walks the fuel, lubricating oil, and cooling water systems for the 1GM10, 2GM20(F), 3GM30(F), and 3HM35(F) marine diesels, from single cylinder to three, in 131 pages of factory procedure.
It covers installation and launching, first start of a new engine, daily operation and stopping, storage, and the full periodical inspection schedule, then closes with troubleshooting charts, piping diagrams for both sea water and fresh water cooling, and A-Type and B-Type electrical wiring diagrams.
The PDF downloads immediately and prints clean, so the air bleeding sequence or the maintenance standard table can sit next to the engine and get oily instead of living on a phone screen.
What's Inside This Yanmar 1GM10–3HM35 Series Operator Manual
| System | Pages | Key Topics |
|---|---|---|
| Name of Parts | 9-12 | Reduction and Reversing Gear, Output Shaft Coupling, Cooling Water Pump, Fuel Injection Pump, Alternator, Starter Motor |
| Engine Specifications | 13-16 | Type, No. of Cylinders, Combustion System, Fuel Injection Timing, Reduction Ratio, Lubricating System |
| Engine Installation | 17-32 | Inspection After Unpacking, Preparation of the Engine Foundation Plate, Propeller, Propeller Shaft, Cooling Wtaer Supply Device |
| After Launching | 33-34 | - |
| Fuel and Lubricating Oil | 35-40 | Selection and Handling of Fuel Oil, Selection of Lubricating Oil |
| Staring the New Engine for the First Time | 41-50 | Supply of Fuel Oil, Supply of Lubricating Oil, Supply of Fresh Water (2GM20F, 3GM30F, 3HM35F), Air Bleeding in the Fuel System, External Inspection |
| Method of Operation | 51-68 | Starting, Cautions After Starting the Engine, Cautions During Operation, Stopping |
| Storage | 69-72 | Storing, Removing Engine From Storage |
| Periodical Inspection and Maintenance | 73-114 | Maintenance Standard, Fuel Oil System, Lubricating Oil System, Cooling Water System, Inspection of Engine Body, Washing the Air Intake Silencer Element |
| Trouble Shooting | 115-124 | Engine Hard to Start, Engine Knocks, Lack of Engine Power, Engine Overheat, Low Lube Oil Pressure, High Fuel Consumption |
| Fuel Oil, Lubricating oil,and Cooling Water Piping Diagram | 125-128 | 1) Sea Water Cooling Type, 2) Fresh Water Cooling Type |
| Electrical Wiring Diagram | 129-130 | 1) A-Type, 2) B-Type |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| All Models | ||
| Wiring cross-sectional area (1+2+3) | < 2.5mm² ~ 20mm² | p. 129 |
| Extension cable total length | less than 6m | p. 129 |
| Fuel filter element replacement interval | Every 250 hrs | p. 75 |
| Alternator belt tension (deflection with 10kg thumb force) | 10mm | p. 107 |
| 1GM10, 2GM20, 3GM30 | ||
| Starter motor power (1GM10, 2GM20, 3GM30) | 12V-1.0kW | p. 13 |
| 3HM35 | ||
| Starter motor power, 3HM35 | 12V-1.8kW | p. 13 |
| 1GM10 | ||
| Number of cylinders, 1GM10 | 1 | p. 1 |
| Continuous rating output (DIN 6270A) | 8.0 Hp/3400 rpm | p. 13 |
| Crankcase lube oil capacity | 1.3L | p. 13 |
| 2GM20(F) | ||
| Number of cylinders, 2GM20(F) | 2 | p. 1 |
| 3GM30(F), 3HM35(F) | ||
| Number of cylinders (3GM30(F), 3HM35(F)) | 3 | p. 1 |
| 1GM10, 2GM20(F) | ||
| Reduction and reversing gear lube oil capacity | 0.25L | p. 13 |
Yanmar 1GM10–3HM35 Series Common Problems This Manual Covers
Cranks slowly or will not start
These engines are unforgiving of voltage drop, and corroded terminals or undersized cable in the starting circuit will leave a healthy engine dead at the key. The wiring diagrams cover both A-Type and B-Type harnesses, with notes on wiring cross sectional area and a total extension cable length limit of 6 meters.
Manual Section: Xii. Electrical Wiring Diagram p. 129Air lock after a fuel filter change
Change a filter or run a tank low and the injection pump delivers nothing until every bubble is out of the lines. Section 6-4 gives the air bleeding procedure in order, so you work the fittings by the book instead of cranking and hoping.
Manual Section: Vi. Staring the New Engine for the First Time p. 41Overheating on the raw water side
A tired impeller or fouled cooling passages push temperature up long before anything obvious fails. The cooling water system maintenance procedures in section 9-3 cover the sea water cooled engines and the fresh water cooled F versions.
Manual Section: Ix. Periodical Inspection and Maintenance p. 73Slack alternator belt and weak charging
A loose or glazed belt quietly undercharges the batteries until the starter tells you about it. The maintenance section gives the check to do by measurement, belt deflection of 10mm under about 10 kg of force, rather than a guess by feel.
Manual Section: Ix. Periodical Inspection and Maintenance p. 73Corrosion and sticking after winter layup
An engine laid up wet with sea water still in the passages comes out of storage with pitted parts and stuck valves. The storage section covers both laying the engine up properly and the steps for removing it from storage in spring.
Manual Section: Viii. Storage p. 69Knocking, lost power, or high fuel consumption
When the engine knocks, runs down on power, or starts drinking fuel, the troubleshooting charts work from symptom back to cause. The same charts cover hard starting, overheat, and low lube oil pressure.
Manual Section: X. Trouble Shooting p. 115Frequently Asked Questions
Which engines does this manual cover?
The Yanmar 1GM10 single cylinder, the two cylinder 2GM20 and 2GM20F, and the three cylinder 3GM30(F) and 3HM35(F) marine diesels. The Engine Specifications section lists type, combustion system, fuel injection timing, reduction ratio, and lubricating system details for each model. p. 13
Is this a workshop manual or an operator manual?
It is the factory operator manual, Yanmar publication 128270-4E, 131 pages. It covers installation, first start, operation, storage, periodical inspection and maintenance, troubleshooting charts, piping diagrams, and wiring diagrams. It is not a full teardown workshop manual.
Does it include electrical wiring diagrams?
Yes. The Electrical Wiring Diagram section includes both the A-Type and B-Type diagrams, with notes on wiring cross sectional area and a maximum total extension cable length of 6 meters, which matters because these starting circuits tolerate very little voltage drop. p. 129
What maintenance schedule does it give for the fuel system?
The Periodical Inspection and Maintenance section calls for replacing the fuel filter element every 250 hours, and covers the lubricating oil system, cooling water system, engine body inspection, and washing the air intake silencer element, alongside the maintenance standard table. p. 73
Is this a digital download?
Yes. You get the full 131-page Operator 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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