1988 Yamaha 40hp excelaration problems

[lordangel1]

i have 1988 40hp yamaha and i am having problems excelerating at times. other times when the motor is full throtle its fine for maybe a half hour of use it then backs off and slows down. then when i throtle it up it gives that wa sound and then eventually go back to full throtle. The gas Tank is brand New with hose and the gas filter is brand new, no leaks and the gas line bolb is hard with fresh gas, so i am lost with this..............please help!!