Johnson Outboard 115 HP Troubleshooting

by Ross Glyn
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Johnson, now Johnson/Evinrude, is synonymous with boats and boating. Its engines are known worldwide. However, as with most machines that are exposed to the elements, wear and tear does occur. The problems are relatively easy to troubleshoot, whether it be an issue with the fuel line assembly or an oil leak. Before taking your 115 HP outboard engine in for service, there are a few basic troubleshooting steps you can do on your own.

Step 1

If you have trouble starting the engine, remove the spark plug cover and using the wrench, remove the plug. Check for excessive dirt or corrosion and clean the plug as necessary. Replace the spark plug if needed.

Step 2

If you suspect the motor has a vacuum leak, inspect all the seals between the engine parts. The seals, or gaskets, are about 1/8 of an inch thick and they seal in the oil and fuel. Check for any cracking or chipping around the edges of seals and have them replaced if necessary. Check the plastic fuel pump cover for any cracks as this can also cause a vacuum leak. If you feel uncomfortable replacing the gaskets, take the engine to a qualified marine mechanic. For a better look at the gaskets, have a mechanic open the various engine components.

Step 3

If the engine stutters and dies or fails to start, check to see if there's enough fuel in the tank. Ensure that the fuel lines are free of kinks and leaks and the connections are all secure. Squeeze the rubber fuel primer to check for any resistance. If you feel resistance, it could mean that fuel is not reaching the engine and the fuel line assembly may need to be replaced.

Step 4

Check the engine pressure by removing the spark plug and connecting the compression test gauge to the system. Low pressure in the engine will cause the engine to run sluggishly, or not at all. A normal reading should be between 60 psi (pounds per square inch) and 90 psi. If the reading is lower than this, have a mechanic investigate further.

Step 5

You may notice a small amount of smoke if there is excessive oil leaking. Remove the engine cowling to check for any residual oil on the cowling's interior. If you notice oil, it could indicate that the rings are wearing out. Have a mechanic take care of this for you.

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