35hp Merc Outboard run issues....help!

[Mllanes2004]

Hi all, new to iboats! I have a 35hp early 80's Merc outboard (Ser # A152832), new to me. Problem is that it's hard starting and does not want to stay running, but mostly intermittent. Can get it to run when throttled up but it's spotty, also when trying to go wide open from idle it hesitates and sounds like it's sucking a ton of air with not power increase. New tank, fuel lines, bulb, fuel separator, fuel pump diaghpram. Not noticeable air or fuel leaks. The guy I got it from said it was running fine and then just cut out while on the lake but was able to keep it running by choking it periodically. Fired right up when I brought it home but would not idle properly, possibly had a bad fuel pump diaghpram, which I replaced yesterday. Definitely pumping fuel as I checked it when the fuel lines were off. I'm at a loss..... I have not taken off the carb myself but it seems to be clean and was clearly used before I got it.
Need your help or expertise! Should I dig the carb out and rebuild it?