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Yamaha 25A - User Manual

Yamaha 25A
131 pages
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25A/30A
LIT-18626-04-54
25A
30A
OWNER’S MANUAL
U.S.A.Edition
6L2-9-1H \ 01.4.20 3:05 PM y[W 1 (2,1)

Table of Contents

Questions and Answers

  • B
    Brian HarrisAug 14, 2025
    What to do if my Yamaha 25A starter will not operate?
    • A
      Ashley TaylorAug 14, 2025
      If the starter on your Yamaha Outboard Motor isn't working, several factors could be the cause. First, check the battery condition and ensure it has the recommended capacity. Weak or low battery capacity can prevent the starter from operating. Also, inspect the battery connections for looseness or corrosion; tighten the cables and clean the terminals if needed. A blown fuse in the electric start circuit could also be the culprit; check for any electric overload, repair it, and replace the fuse with one of the correct amperage. Other potential issues include faulty starter components (have it serviced by a Yamaha dealer), the engine stop switch lanyard not being attached (attach the lanyard), or the shift lever being in gear (shift to neutral).
  • R
    ricardo47Aug 20, 2025
    Why does my Yamaha 25A engine vibrate excessively?
    • T
      Thomas MooreAug 20, 2025
      Excessive vibration in your Yamaha Outboard Motor can stem from several issues. A damaged propeller is a common cause, so have it repaired or replaced. Alternatively, the propeller shaft might be damaged, requiring professional service from a Yamaha dealer. Weeds or other foreign matter tangled on the propeller can also lead to vibrations; remove and clean the propeller. Check if the motor mounting bolts are loose and tighten them. Finally, inspect the steering pivot for looseness or damage; tighten it or have it serviced by a Yamaha dealer.
  • B
    Barbara SchmidtOct 30, 2025
    What to do if my Yamaha 25A engine will not start but the starter operates?
    • S
      sean32Oct 30, 2025
      If your Yamaha Outboard Motor's starter operates but the engine doesn't start, consider these possibilities: The fuel tank may be empty, so fill it with clean, fresh fuel. The fuel could be contaminated or stale, in which case, replace it with clean, fresh fuel. A clogged fuel filter could also be the problem; clean or replace the filter. Ensure the starting procedure is correct by reading the 'STARTING ENGINE' section. Other potential causes include fouled or incorrect spark plugs (inspect and clean or replace with the recommended type), incorrectly fitted spark plug caps (check and refit), poor connections or damaged ignition wiring (check wires, tighten connections, and replace worn wires), an unattached engine stop switch lanyard (attach the lanyard), or the shift lever being in gear (...
  • W
    William LesterNov 3, 2025
    Why does my Yamaha 25A Outboard Motor warning buzzer sound, or indicator lamp light?
    • B
      brianna26Nov 3, 2025
      If the warning buzzer sounds or the indicator lamp lights on your Yamaha Outboard Motor, it could be due to several reasons. The cooling system might be clogged, so check the water intake for any restrictions. A low engine oil level could also trigger the warning, so fill the oil tank with the specified engine oil. An incorrect spark plug heat range could be the cause; inspect the spark plug and replace it with the recommended type. Ensure that you are using the specified engine oil; if not, replace it. Contaminated or deteriorated engine oil can also cause this issue, so replace it with fresh, specified oil. Additionally, check if the load on the boat is improperly distributed and distribute it evenly. For issues like a clogged oil filter, malfunctioning oil feed/injection pump, or a faul...
  • M
    Michele LynchNov 9, 2025
    How to fix irregular idling or stalling in my Yamaha 25A?
    • M
      Mary PierceNov 9, 2025
      Irregular idling or stalling in your Yamaha Outboard Motor can arise from several causes. Start by inspecting the spark plugs and clean or replace them if they are fouled or of an incorrect type. Check the fuel system for any obstructions, such as pinched or kinked fuel lines. Ensure you're using clean, fresh fuel; replace contaminated or stale fuel. Clean or replace a clogged fuel filter. If a warning system is activated, identify and correct the underlying cause. Inspect and adjust the spark plug gap if it's incorrect. Look for wear or breaks in the ignition wiring, tighten loose connections, and replace any damaged wires. Make sure the air vent screw on the fuel tank is open, and return the choke knob to its home position. Also, ensure the motor angle is not too high and return it to th...
  • K
    kiddtracyNov 24, 2025
    Why is my Yamaha 25A Outboard Motor losing power?
    • D
      dhartmanNov 24, 2025
      If your Yamaha Outboard Motor is experiencing power loss, several factors could be responsible. Start by checking the propeller for damage and have it repaired or replaced if necessary. Ensure the propeller pitch and diameter are correct for optimal operation. Adjust the trim angle to achieve the most efficient operation. The motor's mounting height on the transom could be incorrect, requiring adjustment. A warning system activation could also cause power loss, so identify and correct the cause of the warning. Other possible causes include a boat bottom fouled with marine growth (clean the boat bottom), fouled or incorrect spark plugs (inspect and replace), weeds tangled on the gear housing (remove and clean), an obstructed fuel system (check for pinched lines), a clogged fuel filter (clea...

Summary

Chapter 1 GENERAL INFORMATION

SAFETY INFORMATION

Essential safety precautions for operating the outboard motor.

FUELING INSTRUCTIONS

Chapter 2 BASIC COMPONENTS

OPERATIONS OF CONTROLS AND OTHER FUNCTIONS

WARNING SYSTEM

Chapter 3 OPERATION

INSTALLATION

Instructions for installing the outboard motor.

FILLING FUEL AND ENGINE OIL

Procedures for filling the fuel tank and engine oil.

PRE-OPERATION CHECKS

Essential checks before operating the outboard motor.

BREAKING IN (RUNNING IN) ENGINE

Guide to the engine break-in period for optimal performance.

STARTING ENGINE

Step-by-step instructions for starting the outboard motor.

WARMING UP ENGINE

SHIFTING

How to shift between forward, neutral, and reverse gears.

STOPPING ENGINE

Procedures for safely stopping the outboard motor.

TRIMMING OUTBOARD MOTOR

How to adjust the outboard motor's trim for optimal performance.

CRUISING IN SHALLOW WATER

How to operate the motor in shallow water conditions.

TILTING UP;DOWN

Instructions for tilting the outboard motor up and down.

Chapter 4 MAINTENANCE

SPECIFICATION DATA

TRANSPORTING AND STORING OUTBOARD MOTOR

PERIODIC MAINTENANCE

Schedule and procedures for regular maintenance tasks.

MAINTENANCE CHART

A schedule detailing maintenance tasks and intervals.

CLEANING AND ADJUSTING SPARK PLUG

CHECKING FUEL SYSTEM

INSPECTING FUEL FILTER

ADJUSTING IDLING SPEED

GREASING

CHECKING PROPELLER

CHANGING GEAR OIL

Steps for changing the gear oil.

CLEANING FUEL TANK

INSPECTING AND REPLACING ANODE(S)

CHECKING BATTERY

Chapter 5 TROUBLE RECOVERY

TROUBLESHOOTING

Table of common problems, causes, and remedies.

IMPACT DAMAGE

STARTER WILL NOT OPERATE

TREATMENT OF SUBMERGED MOTOR

Yamaha 25A Specifications

General IconGeneral
Engine Type2-Stroke
Cylinder(s)2
Fuel Induction SystemCarburetor
Ignition SystemCDI
Gear Ratio2.08:1
Power Output25 hp
Fuel TypeGasoline
Starting SystemManual
LubricationPremix
SteeringTiller
Trim MethodManual
Oil Tank CapacityN/A (Premix)

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