1988 Yamaha 150 V6 Outboard Motor Service Manual

The 1988 Yamaha 150 V6 Outboard Motor is a powerful 150-horsepower marine engine featuring V6 configuration, oil injection system, electric start, power trim and tilt, CD ignition system, thermostatically controlled cooling, and corrosion-resistant construction. This service manual covers maintenance procedures, troubleshooting, repair instructions, and specifications for proper servicing. Below are key sections for safety, specifications, maintenance, troubleshooting, and repair procedures.

1. Specifications 2. Safety Precautions 3. Maintenance Schedule 4. Engine Components 5. Fuel System 6. Ignition System 7. Cooling System 8. Electrical System 9. Lower Unit 10. Troubleshooting 11. Torque Specifications

Specifications

Technical specifications for the 1988 Yamaha 150 V6 Outboard Motor.

Specification	Details
Engine Type	V6, 2-stroke outboard
Displacement	1596 cc (97.4 cu in)
Bore x Stroke	66.0 mm x 58.0 mm
Compression Ratio	6.5:1
Fuel System	Oil injection with 6 carburetors
Ignition System	CDI (Capacitor Discharge Ignition)
Starting System	Electric start
Gear Ratio	1.86:1
Weight	Approx. 198 kg (436 lbs)
Full Throttle RPM	4500-5500 RPM

Safety Precautions

Essential safety procedures for servicing and operating the outboard motor.

Disconnect battery cables before performing any electrical work.
Work in well-ventilated area when handling fuel or battery.
Use proper lifting equipment for engine removal/installation.
Wear safety glasses and protective gloves during maintenance.

WARNING! Gasoline is highly flammable; no smoking or open flames near fuel system. Always disconnect spark plug wires when working on ignition system.

Maintenance Schedule

Recommended maintenance intervals for optimal performance.

Every 100 hours: Change gear case oil, inspect spark plugs.
Every 200 hours: Clean fuel filter, check water pump impeller.
Every 300 hours: Replace water pump impeller, inspect thermostats.
Annual: Flush cooling system, check corrosion protection anodes.
Seasonal: Lubricate all grease points, check propeller for damage.

CAUTION! Use only Yamaha-approved lubricants and replacement parts.

Engine Components

Cylinder Block: V6 configuration with 6 cylinders
Crankshaft: Forged steel, 7 main bearings
Pistons: Aluminum alloy with 2 compression rings, 1 oil ring
Cylinder Head: Aluminum with sodium-filled exhaust valves
Carburetors: 6 constant velocity type with choke system
Exhaust System: Through-propeller exhaust with water injection
Cooling System: Thermostatically controlled raw water cooling

Fuel System

Fuel delivery and oil injection system components and service procedures.

Fuel Pump: Diaphragm type, engine pulse operated
Carburetors: Synchronization procedure and float level adjustment
Oil Injection: Check oil pump cable adjustment and oil line routing
Fuel Filter: Replace element and clean sediment bowl
Fuel Lines: Inspect for cracks and proper routing

Tip: Always use fresh fuel and Yamaha 2-stroke oil for optimal performance.

Ignition System

CD ignition system testing and component replacement.

Spark Plugs: NGK BU8H, gap 0.9-1.0 mm
Ignition Coils: Primary resistance 0.18-0.24 ohms, secondary 3.7-4.5 kΩ
CDI Unit: Test stator output and trigger coil resistance
Timing: Set at 5° BTDC at idle, 25° BTDC at WOT
Spark Advance: Verify mechanical advance operation

WARNING! High voltage present in ignition system. Disconnect battery before testing.

Cooling System

Raw water cooling system maintenance and repair.

Water Pump: Impeller replacement procedure and housing inspection
Thermostats: Two thermostats, open at 52-57°C (125-135°F)
Pressure Control Valve: Test and replace if leaking
Tell-tale: Verify water flow from indicator hole
Flushing: Use freshwater flush attachment after saltwater use

Electrical System

Charging, starting, and control systems.

Component	Specification
Starter Motor	12V, 1.4 kW
Alternator	12V, 16 amp output
Battery	12V, minimum 70 Ah
Voltage Regulator	Regulated to 14.2-14.8V
Trim/Tilt Motor	12V, 8 amp maximum

Lower Unit

Gear case service and propeller information.

Gear Oil: Capacity 650 ml, use Yamaha Gear Case Oil
Propeller: Standard 13-1/4" x 17" 3-blade aluminum
Shift Mechanism: Check shift rod height and adjustment
Bearings: Inspect water pump bearing and prop shaft bearing
Seals: Replace prop shaft seals and drive shaft seals during service

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	Fuel, spark, or compression	Check fuel delivery, spark at plugs, compression test
Poor acceleration	Carburetion or ignition timing	Sync carburetors, check timing advance
Overheating	Water pump or thermostat	Replace water pump impeller, test thermostats
No charging	Stator or regulator	Test stator output, check regulator connections
Vibration	Propeller or engine mount	Inspect propeller for damage, check engine mounts

Torque Specifications

Critical fastener torque values for proper assembly.

Component	Torque Value
Cylinder Head Bolts	23-25 ft-lbs (31-34 Nm)
Spark Plugs	18-22 ft-lbs (24-30 Nm)
Flywheel Nut	90-108 ft-lbs (122-147 Nm)
Propeller Nut	45-55 ft-lbs (61-75 Nm)
Gear Case Drain/Fill	5-7 ft-lbs (7-10 Nm)
Main Bearing Cap	33-36 ft-lbs (45-49 Nm)

Service Support: Contact Yamaha Marine at 1-800-892-9262 or visit www.yamaha-motor.com