HELP!!! PLEASE

[C YENSEN]

OK GUYS, WELL I AM STILL HAVING PROBLEMS WITH THE MOTOR (1984 470 MERCRUISER)

SHE STARTS FINE, SHE IDLES FINE, AND THEN I TRY TO TAKE HER UP TO SPEED (3900 RPM) AND SHE WILL RUN AT THAT RPM FOR 2 TO 4 MINUTES THEN SHE GIVES OUT. IT SOUNDS LIKE SHE IS STRUGGLING TO GET FUEL. SHE GOES FROM RUNNING GREAT ONE SECOND TO SPITTING AND SPUTTERING AND CHOKING HERSELF OUT. AFTER SHE HAS HER FIT, SHE WILL NOT GO BACK UP OVER 3100 RPM. SATURDAY AFTER SHE HAD HER FIT, I TRIED TO FORCE HER BACK UP TO SPEED AND THERE WAS A PINGING COMING FROM THE CARBURATOR (LIKE THERE WAS SOMETHING LOOSE INSIDE)

I HAVE REPLACED:

SPARK PLUGS
WIRES
POINTS
CONDENSOR
ROTOR
ALL FUEL LINES
FUEL FILTER (TWICE)

FOR THE FEW MINUTES THAT SHE IS RUNNING WELL THE MOTOR SOUNDS VERY STRONG, BUT AFTER SHE HAS HER FIT, SHE RUNS VERY ROUGH (LOT OF SHAKING)

COULD IT BE THE FUEL PUMP?? I CAN REPLACE THAT, BUT IF IT IS A PROBLEM WITH THE CARB, I WILL HAVE TO TAKE IT SOMEWHERE. I REALLY DON'T THINK I KNOW ENOUGH TO TEAR A CARBERATOR APART.

ANY SUGGESTIONS WOULD BE AWESOME.

I AM READY TO PULL MY HAIR OUT ON THIS ONE. STRIPER SEASON IS GOING BY QUICKLY AND IT IS ALMOST TIME TO WINTERIZE HER AND I WANT TO GET THIS PROBLEM FIXED BEFORE THE SPRING

THANKS GUYS