Why does the Mercury outboard run rough at idle?

Are you noticing that your Mercury outboard engine is running rough at idle? If so, there could be several reasons why. In this article, we’ll explore some of the possible causes and solutions to help you get your outboard running smoothly again.

One possible reason for a rough idle could be dirty fuel. If the fuel filter is clogged or the fuel is old and contaminated, this could cause the engine to run poorly. To fix this issue, first, check the fuel filter and replace it if necessary. Then, add fresh fuel to the tank to ensure the engine is getting clean fuel.

Another possible cause of a rough idle is an issue with the spark plugs. If the spark plugs are fouled or worn, this could cause the engine to run poorly. To fix this issue, remove the spark plugs and check their condition. If they are fouled, clean or replace them. If they are worn, replace them with new ones.

A third reason for a rough idle could be a problem with the carburetor. If the carburetor is dirty or misadjusted, this could cause the engine to run poorly at idle. To fix this issue, clean the carburetor and adjust it according to the manufacturer’s specifications.

Lastly, an issue with the engine’s compression could cause it to run rough at idle. If the engine has low compression, this could cause a lack of power and rough running. To diagnose this issue, you will need a compression tester to check each cylinder’s compression. If you find low compression, you may need to repair or replace the engine’s components to restore proper compression.

A rough idle on your Mercury outboard engine could be caused by several factors, from dirty fuel to worn spark plugs to an issue with the carburetor or engine compression. To diagnose and fix the issue, it’s essential to identify the root cause and take the proper steps to solve the problem. With a little bit of troubleshooting and some careful attention to detail, you can get your outboard running smoothly again in no time!

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