1. Float Valve Adjustment: The float valve regulates fuel flow into the carburetor. If it is not properly adjusted, it may allow excess fuel to enter the carburetor, causing it to overflow and leak out the vent tube. Check and adjust the float valve to ensure it is set at the correct level for your specific outboard model.
2. Float Valve Seat Damage: The float valve seat may be damaged or worn, allowing fuel to leak past the float valve. Inspect the float valve seat for any damage or deformation. If it is damaged, it will need to be replaced to stop the fuel leak.
3. Fuel Pump Diaphragm Failure: If the diaphragm in the fuel pump fails, it can cause the pump to deliver excessive fuel to the carburetor, leading to fuel overflow and leakage out the vent tube. Check the fuel pump for any damage or tears in the diaphragm. Replace the diaphragm if it is damaged.
4. Blocked Fuel Line Vent: The fuel line vent provides an escape route for excess fuel and air. If this vent is blocked or restricted, it can cause the carburetor to overfill and leak out the vent tube. Make sure the fuel line vent is clear and unobstructed.
5. Overtightened Float Bowl Bolts: Overtightening the float bowl bolts can cause the float bowl to become deformed, leading to fuel leakage from the vent tube. Check the float bowl bolts and ensure they are tightened to the proper torque specifications.
If the leak persists after checking and addressing these potential issues, it's recommended to seek assistance from a certified marine mechanic with experience working on Mercury outboards. They can further diagnose the problem and perform any necessary repairs or adjustments.
