Part of the Yanmar Repair Manuals.
With the head off a Yanmar 6LY(M)-UTE or 6LY(M)-STE and six valve seats showing recession, the question is not whether to recondition but where the limits sit. This service manual (Yanmar publication HINSHI-H7004, 120 pages) lays out those limits: inspection and service procedures for the cylinder head, pistons and pins, connecting rods, cylinder sleeves, crankshaft and main metal, camshaft and tappets, timing gear, cylinder block, lube oil system, cooling water system, fuel oil system, electrical equipment, marine gears, turbocharger, and intercooler.
It walks the full disassembly and reassembly of this six-cylinder marine diesel, then backs the procedures with standard service data, adjustment check points, and main bolt and nut tightening torques. Troubleshooting charts cover sudden stops, uneven cylinder output, poor exhaust color, and turbocharger and marine gear trouble.
If you are alone at the stand with no dealer to call, this is the reference that gets the engine back together to spec.
What's Inside This Yanmar 6LY(M)-UTE, 6LY(M)-STE Manual
| System | Pages | Key Topics |
|---|---|---|
| Specifications | 5-7 | Principal Specifications, Identification of Important Parts |
| Performance Curves | 8-9 | Specific Fuel Consumption, Torque, Output |
| Disassembly and Reassembly | 10-34 | Preparation Before Disassembly and Reassembly, Tools and Measurement Instruments, Assembly Procedure |
| Engine Component Inspection | 35-55 | Cylinder Head, Piston and Piston Pin, Connecting Rod, Cylinder Sleeve, Crankshaft and Main Metal, Cam Shaft and Tappet, Timing Gear, Cylinder Block |
| Lubrication & Cooling Systems | 56-69 | Lube Oil System, Cooling Water System |
| Fuel & Electrical Systems | 70-86 | Fuel Oil System, Electrical Equipment |
| Marine Gears & Turbocharger | 87-107 | Marine Gears, Turbocharger |
| Troubleshooting | 108-112 | The Engine Suddenly Stops, Cylinder Output Is Uneven, Poor Exhaust Color, Trouble with the Turbocharger, Trouble with Marine Gear, Miscellaneous Trouble |
| Standard Service Data | 113-117 | Adjustment Data Check Points, Important Reference Data at Assembly |
| Main Bolt and Nut Tightening Torque | 118-119 | General Tightening Torque, Tightening Torques, Standard Tightening Torque |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Seawater pump water pressure test | 4kg/cm² | p. 63 |
| Oil filter replacement schedule | Every 250 hours | p. 60 |
| Thermostat valve-opening temperature | 76.5±2°C | p. 115 |
| Thermostat valve lift (at 90°C) | 10mm | p. 115 |
| Number of cylinders | 6 | p. 1 |
| Max speed at no load | 3720 ± 25 rpm | p. 5 |
| Min speed at no load | 700 ± 25 rpm | p. 5 |
| Lube oil delivery | ≥5670 at 3200rpm | p. 6 |
| Lube oil pressure | 0.441 ± 0.049 MPa | p. 6 |
| Main bearing cap tightening torque | 24 ± 1 kgf-m | p. 50 |
Yanmar 6LY(M)-UTE, 6LY(M)-STE Common Problems This Manual Covers
Valve seat wear and power loss
Worn valve seats on these engines show up as falling compression, down-on-power running, and rising oil consumption. The cylinder head inspection procedures give you the measurement points and service limits to decide between reconditioning and replacement.
Manual Section: 4. Inspection and Service Procedure for Each Part p. 35Overheating and intermittent shutdowns
Overheating that comes and goes usually traces to a blocked cooling passage, a failing seawater pump, or a lazy thermostat. The Cooling Water System procedures cover inspection of these parts, and the Standard Service Data lists the thermostat valve-opening temperature at 76.5 ± 2°C.
Manual Section: 4. Inspection and Service Procedure for Each Part p. 35Low lube oil pressure
Pressure below the normal 0.441 ± 0.049 MPa at 3000 rpm points to the oil pump, relief valve, or a clogged filter; the manual specifies oil filter replacement every 250 hours. The Lube Oil System procedures show how to inspect each part in turn.
Manual Section: 4. Inspection and Service Procedure for Each Part p. 35Crankshaft and main bearing wear
A knock under load or metal in the oil means measuring the crankshaft and main metal against the wear limits before ordering parts. The manual gives the inspection procedure and the bearing cap tightening torque of 24 ± 1 kgf-m for reassembly.
Manual Section: 4. Inspection and Service Procedure for Each Part p. 35Poor exhaust color or uneven output
Smoke and rough running on a 6LY(M) can come from fuel delivery, compression, or air-side problems, and guessing wastes parts. The troubleshooting charts work through uneven cylinder output and poor exhaust color cause by cause.
Manual Section: 5. Troubleshooting p. 108Turbocharger trouble
Boost loss, oil carryover, or noise from the turbocharger needs a systematic check before you condemn the unit. The troubleshooting section has a dedicated chart for turbocharger trouble, and the inspection procedures cover the turbocharger itself.
Manual Section: 5. Troubleshooting p. 108Marine gear problems
Hard shifting or slip in the marine gear is covered by its own troubleshooting chart, with inspection procedures for the gear elsewhere in the manual. The torque section also lists tightening torques specified for the marine gear.
Manual Section: 5. Troubleshooting p. 108Frequently Asked Questions
Which engines does this manual cover?
It covers the Yanmar 6LY(M)-UTE and 6LY(M)-STE six-cylinder marine diesel engines. It is Yanmar service manual publication HINSHI-H7004, 120 pages, in English.
Does it include tightening torque specs?
Yes. The Main Bolt and Nut Tightening Torque section lists main bolt and nut torques, general torques, and torques specified for the marine gear. Torques also appear in the reassembly procedures, such as the main bearing cap at 24 ± 1 kgf-m. p. 118
Does it help diagnose running problems?
The Troubleshooting section works through the engine suddenly stopping, uneven cylinder output, poor exhaust color, turbocharger trouble, marine gear trouble, and miscellaneous faults, so you can trace a symptom to a cause before pulling anything apart. p. 108
Are service data and clearances included?
Yes. The Standard Service Data section collects standard service data, adjustment data check points, and important reference data at assembly, including the thermostat valve-opening temperature of 76.5 ± 2°C. p. 113
How is this Yanmar 6LY(M)-UTE Service Manual delivered?
Immediate download of the complete 120-page searchable Service Manual (11 MB). Access it on any device, from a laptop at your desk to a phone in the field.
Can I print specific sections of this Service Manual?
Yes, print as many copies as you want, and there are no restrictions. Many mechanics print the section they need and bring it to the shop floor.
Does this Yanmar 6LY(M)-UTE manual have electrical schematics?
Yes. The Fuel & Electrical Systems section at p70-86 carries the electrical wiring diagrams for this machine.
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