Hello,
Have you tried another fuel tank and hose or pumping the bulb while running?
The next thing to check would be the fuel pressure of the lift fuel pump at high speed, it should be 2-3 psi and remain steady. To do this you would need a clear hose with a T in it to install the gauge and put it between the lift fuel pump and the carb. The clear hose should show solid fuel with no air bubbles - air bubbles would indicate a bad connection between the pump and the tank. All new hose connections must be leak free.
If everything checks out then the carb would be the next thing to look at.
Marine Mechanic
30 Year Service Tech Gas/Diesel.