Mariner 220hp V6 EFI stalling issue/fuel pump

Hey, I have a 1989 or 1990 Mariner 220hp V6 EFI that I am having a few issues with lately. The engine seems to stall when put into neutral and is running poor. I took the boat out last weekend to the dam skiing it just did not have the power at wide open throttle, it then was hard to start and dying out. The primer bulb seem to be soft sometimes and when it is about to stall if pumped it sometimes lasts a little longer. The pump at start up has been playing up, sometimes not coming on to pressurise and other times it does. Is this the fuel pump that needs replacing? I am looking for another engine a used Optimax 250 L but having trouble finding one in Australia and still would like to use the boat but don't want to be wasting money trying to fix the old one and buying new fuel pumps if it wont fix it. Anyone have any idea whats going on. Thanks

You could have either a high pressure pump problem or driver circuit in ECU going bad. Disconnet the black wire from pump and install a ground directly from engine to pump, this allow pump to run ful pressure all the time for testing only. If problems go away the ECU will need replaced...