1996-2006 Yamaha Marine Outboard Motor 20V, 25V, 25V2 Factory Service Manual
Yamaha Models Covered & Key Technical Specifications
Models: Yamaha 20V, 25V, 25V2
Sub-models / Variants: 20DM, 20DMO, 20DEM, 20DEMO, 20DERO, 20MH, 20MH2, 20EH, 20EH2, 25NM, 25NMO, 25NEMO, 25NE, 25NEO, 25NERO, 25MH, 25MH2, 25EH, 25ER
Trade Names: Yamaha Marine Outboards
Model Years: 1996–2006
Serial Numbers: S: 003378–481148, L: 304074–481148
Technical Data:
- Engine type: 2-stroke in-line 2-cylinder
- Total displacement: 395 cm³ (24.11 cu. in)
- Bore x Stroke: 67.0 x 56.0 mm (2.64 x 2.20 in)
- Compression ratio: 7.20
- Maximum output: 18.7 kW (25 HP) at 5,500 rpm
- Gear ratio: 2.08 (27/13)
- Gear oil capacity: 370 cm³ (12.51 US oz)
- Spark plug (Standard): NGK B7HS-10 (BR7HS-10 for Canada and Europe)
- Idle speed: 750 ± 50 rpm (780 ± 30 rpm for Canada)
- Propeller nut torque: 35 Nm (25 ft-lb)
Yamaha Manual Features & Content Preview
- Covers 1996–2006 Yamaha Marine 20V, 25V, and 25V2 outboard models (tiller, remote, manual, and electric start variants)
- Original OEM publication P/N LIT-18616-01-66 (First edition, July 1996)
- 806-page foundational reference providing original specifications for the 6L2 and 6L3 model codes
- Contains 47 detailed exploded-view diagrams and 32 system-specific removal and installation charts
Technical Documentation Overview
This manual details the mechanical and electrical architecture of Yamaha's 20V and 25V 2-stroke outboard motors. The documentation follows a logical, shop-friendly structure. It begins with general information and serial number block identification before moving into crucial handling guidelines. Proper workshop safety protocols must always be observed when working around marine fuel systems and high-voltage ignition components.
From there, individual chapters break down the power unit, lower unit, bracket assembly, and electrical systems. Each section relies heavily on visual exploded-view diagrams paired with specific removal and installation sequences. This visual approach makes it much easier to track complex tear-downs directly on the workbench.
Specification and Data Highlights
Diagnostic work relies heavily on accurate tolerance charts. You will find complete data covering cylinder bore wear limits, piston-to-cylinder clearances, and ring end gaps. For example, the second piston ring end gap is firmly documented at 0.40 to 0.60 mm. The fuel system section features full carburetor assembly diagrams and needle valve inspection parameters, while fuel pump maintenance is supported by detailed diaphragm integrity checks. Ignition timing is specified for both fully advanced and retarded states.
Lower unit maintenance outlines exactly what is needed for gear case lubrication and assembly. The pinion nut torque is listed at 51 Nm, and the propeller shaft housing torque sits at 35 Nm. Intake manifold reed valve stopper height is defined at 6.0 ± 0.2 mm. Having these precise factory specifications on hand eliminates guesswork and prevents costly reassembly errors in the shop.
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