i just purchased a 78 manatee 19 ft. cuddy with a 2000 johnson 90 hp outboard. took her out for a shakedown, and my primer bulb sucks shut above 1500 rpm. once at 1000 rpm. tried running her with fill cap off, but no change.after sitting a few minutes, the bulb opens back up and engine starts right up. looked at old th8reads, and will check my filter and bulb direction.dont want to throw money at the problem, so any advise as to what else to check?