How to Repair a Yamaha Boat Motor

Written by brianna byrne
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How to Repair a Yamaha Boat Motor
Though general repair tips are the same, specific parts vary according to outboard motor make and model. (rainforest motorboat image by Sophia Hendrick from Fotolia.com)

Yamaha's line-up of outboard boat motors has continued to grow since the company first started producing them in 1984. In 2011, the company offered 12 types of outboard motors, each with its own array of different power classes and models. Despite this great variety in outboard motor makes and models, the company offers similar troubleshooting tips for all of its outboard motors. Minor repair instructions can be found in all Yamaha outboard motor owner's manuals.

Skill level:
Moderate

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Things you need

  • Multimeter
  • Replacement fuse
  • Wrench
  • Solvent and wire-bristle brush
  • Replacement battery
  • Battery charger
  • Unleaded gasoline
  • Spark plug wrench
  • Replacement spark plugs
  • Spark plug gap tool

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Instructions

    Starter Problems

  1. 1

    Use the starter. If the engine does not turn over at all, there is likely something wrong with the starter motor.

  2. 2

    Ensure that the shift lever is in "Neutral." If not, the starter motor cannot work.

  3. 3

    Check the main fuse, located inside the motor's main case. Carefully remove the fuse with pliers and connect it to a multimeter. If the multimeter reads anything other than zero ohms, replace it with a new fuse. The type of fuse needed for a particular outboard motor can be found in the "Specifications" section of the owner's manual.

  4. 4

    Check the battery next, also located inside the motor's main case. Remove the battery from its housing, taking care to undo the negative (-) battery terminal first and the positive (+) terminal second.

  5. 5

    Once the battery has been removed, examine the battery terminals.

  6. 6

    Scrape away any corrosion from the battery terminals using a solvent and a wire-bristle brush.

  7. 7

    Replace the battery with a battery of the same capacity if it is damaged.

  8. 8

    Charge the battery fully using a separately-powered charger.

  9. 9

    Reinstall the battery, this time installing the positive (+) battery cable first and the negative (-) cable second.

  10. 10

    Operate the starter. If it still won't work, take the outboard to a certified dealer for inspection.

    Engine Runs Erratically

  1. 1

    Check fuel levels if the engine stops, stalls, or will not start. If the fuel tank is empty, fill it with fresh, unleaded gasoline.

  2. 2

    Check the condition of the fuel if the fuel tank has adequate levels. If the gasoline appears watery, grimy, or gummy, the fuel may be contaminated. Take the outboard motor to the shop to have the fuel tank drained.

  3. 3

    Inspect the spark plugs, located inside the engine's cylinders. The exact type and number of plugs varies according to outboard make and model.

  4. 4

    Remove the spark plug cap to access the spark plug in the cylinder(s). Using a spark plug wrench, gently turn each spark plug counterclockwise and lift it away from the cylinder.

  5. 5

    Replace the spark plug if the electrode end is cracked, white and brittle, or burnt. The exact type of spark plug is listed in the "Specifications" section of that particular outboard's owner's manual.

  6. 6

    Set the spark plug gap to the distance specified in the "Maintenance" section of the owner's manual. To shorten this gap, press the hook-end of the spark plug against a hard, flat surface. Use a spark plug gap tool to pull the hook-end wider to lengthen this gap.

  7. 7

    Reinstall the spark plug, turning it clockwise into the cylinder with a spark plug wrench and returning the spark plug cap.

  8. 8

    Restart the engine. If problems persist, take the outboard in for repairs.

    Excessive Motor Vibration or Heat

  1. 1

    Check the condition of the propeller, located at the bottom of the outboard motor.

  2. 2

    Take the boat motor to the shop if the propeller is cracked or otherwise damaged, or if the propeller shaft is damaged or bent.

  3. 3

    Remove weeds and other debris from the propeller if it is tangled with foreign matter.

  4. 4

    Tighten the motor mounting bolt using a standard wrench.

  5. 5

    Inspect the steering pivot, located on the boat-side of the outboard motor. If it is loose, tighten it with a wrench. If it is damaged, take the outboard to the shop.

Tips and warnings

  • Yamaha recommends that only a certified dealer handle serious repairs and extensive part replacements.
  • Because gasoline releases explosive fumes, you should not smoke or work near an open flame while handling gasoline or inspecting the fuel system.
  • Battery acid can cause burns, so wear gloves and goggles while inspecting and handling the outboard's battery.
  • To avoid engine damage, use only the parts listed in a particular motor's owner's manual.

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