1997 40-hp Mercury Outboard Troubleshooting

The 1997 Mercury 40-hp outboard can bring you hours of excitement and fun in lakes, rivers and other waterways. But a malfunctioning engine can also bring headaches. Routine maintenance can usually keep your outboard motor running smoothly, but if it does act up, follow some troubleshooting procedures to diagnose and fix the problems. Most common outboard issues are either compression or fuel related. Troubleshooting and making your own repairs will save money on marine repair shop costs.

Things You'll Need

  • Ratchet wrench with spark plug socket
  • Compression test gauge
  • Spray carburetor cleaner
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Instructions

    • 1

      Check to make sure there is enough fuel in your outboard's gas tank. Also examine the primer bulb to make sure it collapses easily when you squeeze it in your hand. If the ball has resistance, fuel may not be reaching the carburetor and engine. If this is the case, swap it out with a new primer bulb.

    • 2

      Check the spark plug on your Mercury outboard. If it is dirty, or discolored, it may need to be replaced. Use a plug wrench to remove and install the new spark plug.

    • 3

      Remove the spark plug and place a compression test gauge into the spark plug socket. The compression reading should be approximately 50 to 80 psi. If it is not, it means the rings on your outboard may be bad. If this is the case, have a certified mechanic examine the motor.

    • 4

      Inspect the inside of the top engine cover for signs of oil leakage or spray. This too is a sign that the motor's rings may be bad.

    • 5

      Spray the carburetor with spray carburetor cleaner and also try to add some fuel straight into the carburetor. This can help to unclog fuel lines that may have built up residue.