54 Merc stumbles from a dead stop

[JMFL36]

I've got a 54 Mercury with original 256 Y block and auto ******. Car runs great at speed with good acceleration. My problem is when I'm at a complete stop, like at a light, then take off. The car stumbles badly (and sometimes stalls) until I get up to about 10-15 MPH, then it evens out and runs strong. The car is 6V positive ground, has pertronix ignition, and a new vacuum advance diaphragm. Any suggestions? Thanks, John

 

[wellcraft17]

Check your accelerator pump in the carb , should be a squirt of gas coming out of the nozzle in the Venturi when you press the gas pedal as you take off from a stop.

 

[scicala]

That's what it sounds like to me too.

Sal

 

[jayvee34]

That would be the first thing I would look at.