First! I know this is a boat but it is a GMC Engine. Compression is 150 to 165. Engine starts right up idles good will excel to 4500 if going up slow but moderate to hard excel will bog and die unless I let up on excel. It has a point dist set at 36 dwell. Timing 4 degrees btc at 500 to 600 rpm, (advance is mechanical only no vacuum) 12 degress at 3000 rpm. New points, plugs, wires, cap, rotor condensor, fuel pump, (5.5 psi at idle. Fills 16 oz container in 20 seconds) filters, new gas, checked anti syphon ball and pick up tube screen. Removed wires from coil to eleminate neutral and shift switches as a possible cause, Hot wired coil no help. Had carb rebuilt, still same bogs and dies unless I let up on excel.
Any Ideas would be great, Thanks