I just purchased a 1990 bass buggy with 60 HP Johnson TJ60TLESM. The motor starts and runs fine at mid range on down. If I open the throttle all the way it runs great for about ten seconds and then acts like the throttle is intermiitantly being opened and closed. I tryed squeezing the primer bulb while running WOT no change. The bulb gets hard and stays that way for awhile then will quickley collaps. I have taken the VRO off and run it through the trouble shooting chart with a vacuuume and pressure pump. It passed with flying colors. Any ideas would be appreciated.