454xl starts up great than stalls shortly after but responsive to throttle

"I have a single 1993 454xl ca

"I have a single 1993 454xl carb. electric fuel pump with msts ignition. Last week ran the boat all day no problems. Yesterday started engine idled for 5 minutes and then stalled. Started back up and ran for only 10 seconds and the only way i kept it from stalling was by pumping the throttle. I cleaned out both water separators. I opened up the fuel tank filler cap to rule out a vapor lock. Still same issue. I put the boat into gear engaging the neutral switch and turned the ignition on and heard the pump running fine. The Holley carb was just rebuilt this season and checked the sight screws on the sides of the float bowls and both floats moved. The carb had fuel in it and you could see fuel being ejected into the ventures, maybe not enough. The fuel is only a few weeks old and it did same in both tanks. I am assuming the carb is the problem since there was no post ignition or popping. I am also assuming that since the fuel pump sounded the same as it did when the engine ran fine than its fine. I dont have any type of noticable "filter screen" in the two intake ports for the carb. I first want to rule out anything electric. And if its the carb than i might have lost faith in the rebuilding option. Any insight is appreciated, thanks."

"Try this: Pull a plug wire a

"Try this: Pull a plug wire and stick a spare plug on the end. Ground it to the block and have someone fire the motor up. Watch the spark carefully as the motor runs then dies. Did it loose spark FIRST, or did it spark right up until the motor died? That will tell you if its ignition (most likely) or fuel related.

Jeff"

Would i be able to perform the

Would i be able to perform the same spark test by attaching a timing light to one of the wires watching the flash and if the flash stops before stall than its electrical? Also once the bogging down occurs when i pump the throttle it will still rpm up great but as soon as i back off it boggs out. It just seems to me that its starving for fuel. I am going to put a spare edelbrock 4bbl carb on and perform the timing light test. I will post the results.

The timing light will also wor

The timing light will also work. I'd try a fuel pressure test about now--should be about 5 to 7 psig at idle (and cranking).


Jeff

PS: Are you sure the accelerator pump is functioning properly?