Part of the Yanmar Repair Manuals.
Set the valve lash, check the crank endplay, and the next question is always what the book says: this Yanmar service manual (publication HINSHI-H8001) carries the 6LYA-UTE and 6LYA-STE marine diesels from that first check through complete teardown. It works the basic engine parts, fuel injection pump and governor, turbocharger, lubrication, sea water and fresh water cooling, and the electrical system end to end, with wiring and piping diagrams, specifications, and performance curves collected in Chapter 1.
The KMH6A reduction and reversing gear gets its own chapter, and the manual also lists the HSW800A2 and MG5050A gear models. Chapter 10 pulls the whole job together: disassembly order, tools, bolt and nut tightening torques, and test running after reassembly.
It is a 214 page PDF with 75 bookmarks, so from a leaking sea water pump to main bearing clearances, the section you need is two clicks away at the bench.
What's Inside This Yanmar 6LYA Series Manual
| System | Pages | Key Topics |
|---|---|---|
| General | 5-15 | Exterior Views, Specifications, Performance Curves, Dimensions, Wiring Diagrams, Piping Diagrams |
| Inspection and Servicing of Basic Engine Parts | 16-46 | Cylinder Block, Cylinder Sleeve, Cylinder Head, Piston and Piston Pins, Connecting Rod, Crankshaft and Main Bearing, Camshaft and Tappets, Timing Gear |
| Fuel Injection Equipment | 47-86 | Fuel Injection Pump Construction, Fuel Injection Pump Specifications, Fuel Supply System, Fuel Injection Nozzle, Fuel Feed Pump, Disassembly |
| Intake and Exhaust System | 87-100 | Turbocharger |
| Lubrication System | 101-110 | Lube Oil Pump, Lube Oil Filter, Oil Pressure Control Valve, Lube Oil Cooler, Piston Cooling Nozzle, Rotary Waste Oil Pump (Optional) |
| Cooling Water System | 111-125 | Sea Water Pump, Fresh Water Pump, Fresh Water Cooler, Pressure Cap and Sub Tank, Thermostat, Kingston Cock (Optional) |
| Reduction and Reversing Gear | 126-136 | Specification and System, Reassembly and Disassembly (KMH6A), Cautions for Reassembly |
| Remote Control (Optional) | 137-139 | Remote Control System (Option), Remote Control Installation |
| Electrical System | 140-170 | System Diagram, Battery, Starter Motor, Alternator, Instrument Panel, Warning Devices, Tachometer |
| Disassembly and Reassembly | 171-207 | Disassembly and Reassembly Precautions, Disassembly and Reassembly Tools, Bolt/Nut Tightening Torque, Test Running |
| Troubleshooting | 208-213 | - |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Cylinder head bolt tightening torque (First stage) | 15.0~16.0 kg-m | p. 26 |
| Cylinder head bolt tightening torque (Second stage) | 20.0~22.0 kg-m | p. 26 |
| Nozzle fastening nut tightening torque | 0.4~0.5 kg-m | p. 201 |
| Exhaust valve clearance | 0.4 mm | p. 28 |
| Lube oil filter replacement period | Every 250 hours of engine operation | p. 106 |
| Main bearing clearance standard value | 0.036~0.093 mm | p. 204 |
| Cylinder head gasket thickness at tightening | 1.30±0.05 mm | p. 202 |
| Alternator Nominal Output | 12V/80A | p. 155 |
| Thermostat Opening Temperature | 76.5°C | p. 123 |
Yanmar 6LYA Series Common Problems This Manual Covers
Engine loses power under load
A gradual drop in output, most obvious under load, usually traces to fouling on the blower side of the turbocharger rather than a fuel fault. The Intake and Exhaust System chapter covers turbocharger construction, inspection, and servicing so you can clean and verify the unit instead of guessing.
Manual Section: Chapter 4 Intake and Exhaust System p. 87Sea water pump leaks from drain
Continuous dripping from the sea water pump drain during operation means the oil seal is done, not that the pump is weeping normally. The Cooling Water System chapter covers pump disassembly and seal replacement, along with the fresh water pump, fresh water cooler, and thermostat.
Manual Section: Chapter 6 Cooling Water System p. 111Oil consumption climbs at higher RPM
Rising oil use at cruise speed on a high hour engine points to ring, sleeve, or bearing wear. Chapter 2 gives the inspection procedures for the cylinder sleeves, pistons and piston pins, connecting rods, and crankshaft and main bearings, so you can measure the wear and decide how deep the rebuild goes.
Manual Section: Chapter 2 Inspection and Servicing of Basic Engine Parts p. 16Hard starting after fuel filter service
Air pulled into the fuel system during a filter change will keep a 6LYA cranking without firing. The Fuel Injection Equipment chapter covers the fuel supply system, feed pump, fuel filter, injection pump, and nozzles, including disassembly and adjustment of the pump and governor.
Manual Section: Chapter 3 Fuel Injection Equipment p. 47Oil leaks after a filter change
A fresh leak right after an oil service usually comes down to filter seating or sealing rather than a failed gasket elsewhere. The Lubrication System chapter covers the lube oil filter, oil pump, pressure control valve, oil cooler, and piston cooling nozzles.
Manual Section: Chapter 5 Lubrication System p. 101Charging or starting electrical faults
Slow cranking, a dead panel, or a battery that never comes up can hide in several places between the starter and the gauges. The Electrical System chapter carries the system diagram plus service coverage for the battery, starter motor, alternator, instrument panel, warning devices, and tachometer.
Manual Section: Chapter 9 Electrical System p. 140Rough or doubtful gear engagement
When the reduction and reversing gear engages harshly or behaves inconsistently, the fix means opening the gear case correctly. Chapter 7 covers the KMH6A specification and system, its disassembly and reassembly, and the cautions to follow when putting it back together.
Manual Section: Chapter 7 Reduction and Reversing Gear p. 126Frequently Asked Questions
Which engines and gears does this manual cover?
It is the Yanmar service manual (publication HINSHI-H8001) for the 6LYA-UTE and 6LYA-STE marine diesel engines. It also lists the KMH6A, HSW800A2 and MG5050A gear models, with a dedicated chapter on the KMH6A reduction gear. The engine coverage goes to rebuild level - the cylinder head bolt torque is given as a two-stage tightening on page 26.
Does it give the cylinder head bolt torque and sequence?
Yes. Chapter 2 lists the head bolt tightening torque in two stages, 15.0 to 16.0 kg-m first and 20.0 to 22.0 kg-m second, as part of the cylinder head servicing procedure. p. 26
What is the valve clearance for the 6LYA?
The manual lists 0.4 mm for the exhaust valves, and Chapter 2 covers the adjustment procedure along with the rest of the cylinder head servicing. p. 28
Are wiring diagrams included?
Yes. Chapter 1 General includes the wiring diagrams and piping diagrams, and the Electrical System chapter adds the system diagram plus service information for the starter motor, alternator, instrument panel, warning devices, and tachometer. p. 5
How quickly can I access this manual after buying?
Immediate download of the complete 214-page searchable Service Manual. Access it on any device, from a laptop at your desk to a phone in the field.
Am I able to print pages from this manual?
No copy protection at all. The PDF is DRM-free, so print whatever sections you need to take to the shop. Standard letter or A4 paper works.
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