Mercury 4 hp 4 stroke issue

[waterwks4me]

I have a 2010 4 stroke Mercury 4 hp. Idles perfectly and will rev up with no issues but when I put it in gear and give it gas it will run well for about 10 seconds or just enough to get up on a plane and then sputters and stops running, reducing throttle to idle sometimes keeps it running. I have taken the carb apart and flushed it out with carb cleaner two separate times but have not given it a 2 or 3 day soak. Starts like a champ but once given throttle it does the same thing. I feel like it is running off of the fuel in the bowl but then the fuel intake is not enough for the demand. Open to suggestions please

 

[Dekker500]

Sounds like a fuel delivery issue. No specifics, but you can check the following:

• When you have it at full throttle, if you gently pump the primer bulb, will the engine keep going?
• Make sure the fuel tank vent is open (or test drive it with the fuel cap opened a crack). This applies whether using the internal tank or external tank.
• Double-check your fuel hose for possible air leaks. Try it with a friend's known-good fuel hose. For that matter, try it with their tank...
• This model has an integral tank - verify the fuel shutoff valve is set to the correct position. I believe it is UP to close the internal (such as when using an external tank or transporting engine) and DOWN to open the internal (when not using external tank)
• Is it possible there is old fuel in the system? Drain the old gas in the reservoir and re-fill.
• Is your oil pressure indicator light turning on?
• Your model has a fuel line filter. Inspect and possibly replace if you suspect stale fuel was an issue. It could be gummed up, and allow enough fuel through for idle speeds, but not enough at full throttle. Relatively cheap maintenance item to replace.
• Lower probability, but check spark plug for wear and appropriate gap (0.035 / 0.9mm)

 

[waterwks4me]

Dekker, thanks for responding. I have made sure fuel tank vent is openI have removed all fuel and refilled with fresh gas as well as changing out the old fuel filter with a new one. Oil pressure light is not turning on as well as checked oil level. This model has an internal tank with the capabilities of an external tank. I have verified the fuel shutoff valve is in the open position and fuel is flowing to the carb. I checked the fuel pump by running engine with fuel line being collected into a container. Had an even flow but not sure how much should be flowing but at least fuel pump is doing its job. I will replace spark plug with proper gap. Any other suggestions?

 

[Dekker500]

Yikes, that's about it for my KISS principle of troubleshooting.

The only thing I didn't mention is to verify you have the choke knob set the right way... It might start and idle with the choke in either position, but when choked it won't get enough air to handle higher RPMs. For that matter, take the cover off the engine and verify that the choke knob is opening/closing the choke...

If you have a friend with an outboard, you might consider borrowing their tank & hose to test with an external fuel source.

Other than that... I'm out of ideas!

 

[Dekker500]

Oh, one last thing... You mention having cleaned-but-not-soaked your carb. Consider getting a carb kit and replacing the gaskets/seals, and verifying the float.

 

[waterwks4me]

Dekker, thanks for your suggestions.