1996 Mercury 75hp fuel problem

Every tine I run my motor it will run fine for several minutes then big down regardless of how much throttle I give it, when I but the choke it picks up and surges but only for a second and only when I repeatedly push the choke. New filter and I run sea foam in it as well. A good friend recommended spraying QuickSilver Power Tune in the carbs while it was running until it dies then after letting it sit cranking it until it clears. Any help would be appreciated...

 

Pull out the plugs after - are they wet?

What colour are the deposits?

That might give you a clue if too week or too rich.

Can you keep it running if you trickle gas into the carb?

 

Plugs are wet but not really coated with black like I've seen in the past. It idles rough and when I put it in gear it goes takes off but I can push the throttle to the stops and it won't go any faster unless I press the choke. or increase RPMs unless in neutral.

Haven't trickled any gas into the carbs but can keep it running by pressing the choke.

 

That usually means that the jets are clogged. It needs to be cleaned.

 

If you have to richen the mixture, she's lean, which as Gonzo mentions, is typical of varnish deposits in the passages and orifices. A very common problem, especially with ethanol fuels and easily fixed with a disassemble, cleaning and new gaskets.

 

Have you checked the fuel line squeeze bulb. Make sure it is staying hard while the motor is running. If it is not holding pressure the fuel pump can't keep enough fuel up to the carbys.