70 hp hi-speed problem

[cedarman]

I have a 70 hp (1986?), the problem started with the motor working fine then losing power. The fuel primer bulb collasped, and the motor quit. Replaced the fuel line, primer bulb and tank. Now the motor starts and works fine for a short period then it loses power and will only idle, as soon as you give it throttle it boggs and dies. If you start and manually open the throttle at the carbs it seems to have lots of power. Again leave it for a couple of days and it will start and run great full throttle every thing for 3-5 minutes and then lose power again. Any ideas would be appreciated..
Thanks
Cedarman

[gregmccready]

Is this a built in tank or portable, if it is built in check your anti sifen valve on tank. If it is prtable open cap and try running it, if it runs fine it your tank.
Greg

[boats.net]

When the engine is acting up, everytime you manually rev the carburetor, the problem goes away?