Check Float and Float level. My 5.7 with Holley Carb will run fine, but shut off for 15 - 20 minutes, when restarted, it will run, but if WOT is applied it will stumble, big, and Die. I came to the Conclusion that it the fuel system was Vapour Locking or the Carb was Percolating. Both conditions are caused by engine heat. Maybe it gets warmer in the bilge than thought, or the garbage being sold as Gasoline these days is refined for use in a pressurized fuel system and thus less likely to suffer from Vapour Lock and/or Percolation there. Carbs only use Atmospheric Pressure to supply Fuel, and it being lower, the fuel is more likely to Boil