Yanmar SD20, SD30, SD31 Sail Drive Unit Service Manual
This service manual covers the Model SD20, 30 & 31 sail drive unit, providing detailed information on disassembly, reassembly, and maintenance procedures. PN A0A5054-JC03.
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Yanmar Models Covered & Key Technical Specifications
Models: Yanmar SD20, SD30, SD31
Sub-models / Variants: Standard unit, Long-reach unit
Serial Numbers: SD20 #2129 and after, SD30 #0108 and after
Technical Data:
- Reduction gear system: Constant mesh gear with dog clutch
- Reduction ratio (Ahead/Astern): 2.64 (SD20/30), 2.31 (SD31)
- Lubrication system: Splash lubrication
- Lubricating oil capacity: 2.2 liters (Standard unit), 2.5 liters (Long-reach unit)
- Propeller speed (at DIN 6270A): 1289 rpm (SD20), 1212 rpm (SD30), 1472 rpm (SD31)
- M14 nut torque: 6.0 – 7.0 kgf-m
- M10 bolt torque: 2.8 – 3.2 kgf-m
- M12 nut torque: 4.6 – 5.0 kgf-m
- M8 bolt torque: 1.4 – 1.6 kgf-m
- M6 bolt torque: 0.5 – 0.7 kgf-m
Yanmar Manual Features & Content Preview
Yanmar SD20, SD30, and SD31 Sail Drive Service Manual
- Covers 2005 Yanmar SD20, SD30, and SD31 sail drive units, including standard and long-reach configuration variants
- Original OEM publication A0A5054-JC03, printed in Japan
- Includes 15 detailed exploded-view mechanical diagrams and 2 electrical wiring schematic layouts for A-type and B-type instrument panels
- Accessible from your device as soon as the order is placed
- Suitable for printing individual sections for shop-floor use
- Index includes chapters dedicated to shim-based gear backlash adjustment and specialized long-reach unit modification procedures
- This 88-page factory service documentation provides the necessary torque values and clearance specifications for professional sail drive maintenance
Internal Structural Documentation
The 2005 Yanmar SD20, SD30, and SD31 service manual organizes technical procedures into eight primary chapters. Initial sections establish base specifications, tool requirements for disassembly, and criteria for replacing wear-prone components. Subsequent chapters focus on the mechanical breakdown and reassembly of the upper and lower gear cases, detailing the specific shim adjustment protocols required for gear backlash control and bearing fitment.
Final chapters provide instructions for modifying standard sail drive units into long-reach configurations, accompanied by wiring diagrams for instrument panels. The manual concludes with comprehensive torque specifications for all internal fasteners, ensuring precision during reassembly of the dog clutch, pinion shafts, and bearing supports.
Specification and Reference Data
Documentation includes precise torque requirements for critical fasteners, such as 6.0–7.0 kgf-m for M14 lower pinion nuts and 21.0–23.0 kgf-m for M25-thread propeller shaft nuts. Understanding parts documentation for Yanmar marine equipment assists with identifying necessary shim thicknesses for backlash settings (standard 0.1–0.2 mm).
Lubricating oil capacity is documented at 2.2 liters for standard units and 2.5 liters for long-reach models. The 2005 Yanmar SD20, SD30, and SD31 sail drive service manual serves as the primary technical reference for marine technicians, providing engine-matching data and essential service clearances for the full SD-series product line.
Document Reference: Form A0A5054-JC03, Yanmar Diesel Engine Co., Ltd.
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