OK I have a holley 750 setting on top of a 302 in a boat that has been extremely frustrating. It seems to be leaking from the secondaries at idle to the point that fuel pools up on top of the secondary butterflies eventually leaking out of the shaft on the side. Fuel pressure is at 6 psi, and the float level seems OK (a touch low really) via the sight windows on the side of the bowls. There isn't a power valve back there, just one of those jet plates. I'm scratching my head over here.

First guess, fuel valve is not sealing.

Hollies are impossible to set up sometimes. Best luck I has was with "propane enrichment". Your sure to get the throttle plates positioned in the idle system. Not positioned properly could be another reason.