Part of the Yanmar Repair Manuals.
Yanmar's service manual for the D27A and D36A diesel outboards takes both engines from complete teardown to final backlash adjustment, and it earns its keep the moment you have one on a stand with the powerhead open. Chapter 2 sequences the disassembly and reassembly, Chapter 3 walks every engine part (cylinder block, piston and connecting rod, crankshaft, cylinder head, unit injector, governor) through inspection with the measurements to make, and Chapter 4 handles the drive unit from swivel bracket to lower gear case and cooling water pump.
Guessing a torque figure on a flywheel nut or an injector set bolt is how a rebuild fails on the water. Chapter 8 lists the real numbers, and Chapter 7 gives the service standard tables for wear limits.
The 142 pages arrive as one bookmarked PDF (publication A0A5055-JC03), so the section you need, whether that is the wiring diagram, a backlash procedure, or the periodical inspection table, is seconds away.
What's Inside This Yanmar D27A, D36A Manual
| System | Pages | Key Topics |
|---|---|---|
| General | 4-16 | Specifications, Exterior View, Cross-Sectional View |
| Disassembly and Reassembly | 17-59 | Preparations Before Disassembly and Reassembly, Tools, Measuring Instruments and Service Equipment, Exploded View of Parts, Reassembly Procedures |
| Inspection and Service Procedures for Engine Parts | 60-89 | Service Procedures for Engine Parts, Cylinder Block, Piston and Connecting Rod, Crankshaft, Camshaft, Cylinder Head, Valve Arm Case, Intake/Exhaust Valve Arm and Unit Injector |
| Reassembling and Servicing of Drive Unit | 90-110 | Swivel/Steering Bracket, Clamp Bracket, Upper Case, Bottom Cowling and Fitting Parts, Lower Gear Case, Cooling Water Pump and Cooling Water Piping, Steering Handle |
| Piping Diagram | 111-113 | Fuel System Components, Lube Oil System Components, Cooling Water System Components, Thermostat Valve Opening Temperature |
| Electric Equipment | 114-124 | Generator, Starting Motor, Warning Device, Wiring Diagram |
| Service Standard | 125-131 | Service Standard Table |
| Main Bolt Tightening Torque | 132-134 | Engine Bolt Tightening Torque, Drive Unit Bolt Tightening Torque, General Bolt and Nut Tightening Torque |
| Backlash Adjustment | 135-137 | Pinion Gear Backlash Adjustment, Forward Gear Backlash Adjustment, Reverse Gear Backlash Adjustment, Propeller Shaft Backlash Adjustment |
| Periodical Inspection | 138-139 | Periodical Inspection Table |
| Option | 140-142 | Diesel Outboard Propeller Guard Holes |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Injector tap set bolt tightening torque | 2.6~2.8 kgf-m | p. 133 |
| CW pump case tightening bolt torque | 0.7~0.9 kgf-m | p. 133 |
| Overheat alarm buzzer activation | O (activates) | p. 118 |
| Cylinder head temperature OFF | 115°C | p. 119 |
| Crankshaft Side Gap (Standard) | 0.15-0.45 mm | p. 125 |
| Flywheel Tightening Nut Torque | 16.5~17.5 kgf-m | p. 133 |
| Pinion Gear Tightening Nut Torque | 9.0~10.0 kgf-m | p. 133 |
| Backlash between Pinion and Forward Gear (Standard) | 0.1~0.25 mm | p. 129 |
Yanmar D27A, D36A Common Problems This Manual Covers
Hard starting on questionable fuel
These small diesels are sensitive to fuel quality, and a clogged filter, air in the lines, or a fouled unit injector will keep one from firing or let it stall right after start. The inspection procedures for the unit injector and related engine parts show what to check and how to service it.
Manual Section: Chapter 3 Inspection and Service Procedures for Engine Parts p. 60Overheating from a worn impeller
A tired cooling water pump impeller or restricted cooling passages will push temperatures up fast, and neglect here is the quickest way to kill a diesel outboard. The drive unit chapter covers the cooling water pump and cooling water piping along with the lower gear case around them.
Manual Section: Chapter 4 Reassembling and Servicing of Drive Unit p. 90Overheat alarm buzzer keeps sounding
When the warning buzzer trips on high cylinder head temperature, you need to know whether the sensor, the wiring, or the engine itself is at fault. The electric equipment chapter covers the warning device and includes the wiring diagram for tracing the circuit.
Manual Section: Chapter 6 Electric Equipment p. 114Gear whine or harsh shifting
Wrong backlash in the lower unit shows up as whine under load and clunky engagement, and it chews up gears if left alone. This chapter gives the adjustment procedures for pinion, forward, reverse, and propeller shaft backlash.
Manual Section: Chapter 9 Backlash Adjustment p. 135Smoke and rough idle after storage
Stale fuel and deposits from long layup commonly cause exhaust smoke and uneven running on these engines. The piping diagram lays out the fuel, lube oil, and cooling water system components so you can trace lines and bleed points without guesswork.
Manual Section: Chapter 5 Piping Diagram p. 111Worn parts past their limits
Once the engine is apart, every measurement (crankshaft side gap, bore wear, valve components) has to be checked against a number, not a feel. The service standard tables list standard values and wear limits for both the engine and the drive unit.
Manual Section: Chapter 7 Service Standard p. 125Fasteners loosened by a past rebuild
A flywheel nut or pinion gear nut torqued by feel during an earlier repair will eventually work loose or strip. The torque chapter lists tightening values for engine bolts, drive unit bolts, and general fasteners so reassembly holds.
Manual Section: Chapter 8 Main Bolt Tightening Torque p. 132Frequently Asked Questions
Which engines does this manual cover?
It is the Yanmar service manual for the D27A and D36A diesel outboard motors, publication number A0A5055-JC03, covering both the engine and the drive unit across 142 pages in English.
Does it include torque specifications?
Yes. The Main Bolt Tightening Torque chapter lists engine, drive unit, and general fastener torques, including 16.5 to 17.5 kgf-m for the flywheel tightening nut and 9.0 to 10.0 kgf-m for the pinion gear nut. p. 132
Are wear limits and service standards listed?
Yes. The Service Standard chapter has tables for both engine and drive unit, with standard values and limits, for example a crankshaft side gap standard of 0.15 to 0.45 mm. Chapter 9 adds backlash standards such as 0.1 to 0.25 mm between pinion and forward gear. p. 125
Is there a wiring diagram for troubleshooting electrics?
Yes. The Electric Equipment chapter includes the wiring diagram plus service coverage of the generator, starting motor, and warning device, so you can trace an overheat buzzer or a no-crank condition through the actual circuit. p. 114
How quickly can I access this manual after buying?
This is a 142-page searchable PDF ready for immediate download. Works on any device, so pull it up on your phone while you're under the hood. No shipping, no waiting.
Am I able to print pages from this 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.
Is the electrical system covered in this Yanmar D27A Service Manual?
Complete wiring diagrams are included, covering all electrical circuits, harness routing, and connector pinouts for the Yanmar D27A, D36A.
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