Yanmar 1GM10, 2GM20, 3GM30 & 3HM35 Marine Diesel Service Manual — 1980s–1990s

This Yanmar Marine Diesel Engine Service Manual, manual code 0000A0A1361, covers 1GM10(C), 2GM20(F)(C), 3GM30(F)(C), and 3HM35(F)(C) marine diesels. F identifies fresh-water cooling and C a sail-drive engine configuration; an unmarked model uses direct sea-water cooling.

PDF Search, Bookmarks and Wiring Detail

Search and diagram detail: PDF text search is not available. Embedded bookmarks provide access to chapters and major subsections. Small labels in the checked A- and B-type instrument-panel wiring diagrams are readable when enlarged.

The download contains one printable, English-language 463-page PDF, including seven cover/preliminary pages and two rear-cover pages.

Diesel Engine, Fuel System and Marine Gear Repair

These selected repair topics outline the manual’s contents. Other examples include optional bilge-pump specifications and guidance on selecting fuel and lubricating oil.

• Internal-engine repair: Step-by-step teardown and reassembly for direct sea-water and fresh-water engines, with cylinder-head, piston, connecting-rod, crankshaft, bearing, camshaft, and timing-gear service.

• Fuel-system repair: Injection-pump inspection and tester adjustment, injection timing, nozzle spray and seat tests, nozzle-pressure setting, feed-pump service, and governor adjustments.

• Cooling-system work: Rubber-impeller pumps, thermostats, anticorrosion zincs, fresh-water pump inspection, heat-exchanger testing, and conversion from direct sea-water to fresh-water cooling.

• Lubrication, intake and exhaust: Trochoid-pump inspection, filter bypass and pressure-regulator checks, oil-pressure measurement, intake-silencer service, crankcase breathing, and exhaust-component inspection.

• Marine-gear repair: Cone-clutch and multi-disc gear inspection, disassembly and reassembly, bearing and shaft setup, shifting-device service, shim selection, and V-drive backlash adjustment.

• Electrical diagnosis: Battery and starter-motor checks, standard and optional alternator testing, A/B instrument-panel wiring diagrams, warning-device diagnosis, and tachometer tests.

• Factory data and tools: Model-specific torque tables, fits and clearances, wear limits, capacities, electrical test values, packing and adhesive locations, and special-tool information.

Compiled by Yanmar for engineers engaged in sales, service, inspection, and maintenance, it is best suited to trained marine-diesel technicians and experienced rebuilders because material treated as common knowledge is omitted.

Internal Engine Inspection and Reassembly

Cylinder-block coverage includes crack detection, bore measurement, reboring, and oversize-piston data. Cylinder-head service extends to combustion-surface cracking, water-passage corrosion, valve seats and guides, precombustion chambers, and valve-clearance adjustment.

Piston, connecting-rod, crankshaft, and main-bearing sections provide inspection criteria and assembly precautions. Engine cross-sections and the valve-timing diagram accompany camshaft, timing-gear, and flywheel service. Separate engine teardown and reassembly chapters include adjustment requirements and test running after assembly.

Injection Pump, Nozzles and Governor Controls

Fuel-system coverage includes matched plunger/barrel components, the control rack, delivery valves, pump-tester adjustment, nozzle spray assessment, seat-tightness checks, and pressure setting. The governor chapter treats the injection limiter, no-load maximum-speed limiter, idle adjuster, and engine-stop controls.

The injection-pump chapter explains that mixing cylinder-specific parts prevents reassembly without a pump tester, while excessive delivery-valve-holder torque can distort the plunger, increase control-rack resistance, and damage the pump body or valve gasket.

Cooling, Lubrication and Exhaust Service

Direct sea-water and fresh-water cooling diagrams distinguish the two systems and their piping. Coverage includes thermostats, anticorrosion zincs, heat-exchanger cleaning and leakage tests, the filler cap/subtank, and cooling-temperature switches.

The fresh-water pump section specifies inspection and replacement of faulty assemblies rather than internal pump disassembly. A separate conversion chapter covers changing a 2GM20, 3GM30, or 3HM35 to its corresponding F configuration, including operational and leak checks.

The lubrication chapter traces drilled oil galleries and covers primary and secondary oil-pressure measurement. Intake-silencer, crankcase-breather, water-cooled exhaust-manifold, mixing-elbow, and carbon/deposit inspections are also included.

The sea-water pump precautions explain how dry running or turning the engine in reverse can damage the rubber impeller.

Marine Gear Configurations and Sail-Drive Scope

Transmission repair covers KM2-C/KM3-A cone-clutch gears, the 3HM35(F)’s KBW10E multi-disc unit, later KM2P/KM3P gears, and the KM3V V-drive. Clutch, speed, and engine-stop remote controls are treated separately.

Later-gear coverage begins at E/# 03413 for the 1GM10 with KM2P, E/# 03567 for the 2GM20(F) with KM2P, and E/# 01888 for the 3GM30(F) with KM3P, effective from August 1985.

The KM3V section identifies 1GM10V, 2GM20V/2GM20FV, and 3GM30V/3GM30FV applications. Sectional and power-transmission views support V-drive inspection, shaft-shim selection, and backlash adjustment.

Sail-drive coverage is limited: The C-model specification table lists SD20 and SD30 units, but this manual does not contain a dedicated sail-drive disassembly or overhaul chapter.

Electrical Fault Finding and Operating Troubles

Alternator and instrument-panel troubleshooting charts supplement component tests and reassembly checks. Warning-device diagnosis links lamp and buzzer behavior to wiring, switches, and monitored engine conditions, helping distinguish an alarm-circuit fault from the condition it signals.

The operating chapter provides cause-and-corrective-action tables for starting trouble, sudden shutdown, output loss, abnormal exhaust, overheating, oil-pressure problems, and engine knock.

Service Equipment and Factory Precautions

Named tools include main-bearing replacers 124085-92400 and 128670-92400, piston-pin tools 124085-92260 and 128670-92260, valve insertion/extraction tool 124085-92250, and fuel-injection-valve replacer 101104-92180.

For the 3HM35(F), the tool section identifies output-shaft nut wrench 177099-09010 and coupling lock 177099-09020. Measuring-equipment information covers bore, clearance, torque, and injection work.

Follow the factory precautions for hot pressurized coolant, batteries, lifting, and test running before dismantling or servicing the engine.

Cylinder-Head and Timing-Gear Specification Samples

The cylinder-head inspection tables give a distortion wear limit of 0.07 mm for the covered GM and HM engines.

For crankshaft-to-camshaft gear backlash, the maintenance standard is 0.05–0.13 mm and the wear limit is 0.3 mm. These values accompany the timing-gear inspection and measurement procedures.