96 intruder 150 fuel issues

i have a 1996 intruder 150 that is giving me problems
this started last fall and i didnt fix the problem then and the boat sat idle since then. i took it out for the first time last week and it ran great for 3 days in a row and on the fourth it started again. the engine starts fine takes off fine will run wide open without any issues its when i drop her off plane it sounds like its running on 3 cylinders, jump back pump the ball and its fine again this happened 4 times in a row and the it ran fine the rest of that day.
after new primer ball new water sep filter new plugs and new engine filter i took her out on the 5th day same thing runs great at first then pump the ball every time after coming off plane after pumping ball if i give it full throttle it runs great if i stay at idle speed i have to keep pumping the ball to keep it running or hold the choke to get back on plane. once on plane it runs great 5500rpms with a 14-1/2x24 raker on a stratos 295xldc. http://www.bassboatcentral.com/smileys/praying.gif http://www.bassboatcentral.com/smileys/praying.gif HELP

Might try looking at the anti-syphon valve in the top of the fuel tank... knock the little ball out.... and check for air leaks around the fittings.

Just get rid of it, that is what I did. Go to lowes and get a brass fitting to replace the AS valve.

im not sure what this is or looks like,

it's the fitting the fuel line hooks to on the tank,behind the seat,you could get to mine through a cut out in the alum housing,has an omc sign over it,in the middle.check around on the engine and look for gas seepage around the carbs and lines..

thanks i will check it tomarrow