strange problem

My Yamaha 1991 55hp is doing something odd. I can go full throttle for a little while than suddenly it will bog down to about half throttle and i can't get it to go up to that rpm again. When it bogs it bogs down fast too, its not slow it is instant.
My first thought is that it was fuel, i checked the vent in the tank and it isn't clogged (I used an air hose to blow through it and listend to the fill line).
I changed the pump bulb or primer bulb the thing you pump up by hand before you start it. I also changed the remote fuel filter and cleaned the inline one. Than i thought because since i was able to drive around out there for a while before the bog down that it might not be fuel related. If it was dirt in the carb it wouldn't happen like this it would never let me get to the rpms. either way after what i changed it did the same thing again.
Any ideas? i don't know what kind of sensors this engine has or anything.

Re: strange problem

my merc did this to had to clean carbs i guess big trash floats around wile your moving then clogs jets then maybe when you cut off eng trash floats off becouse no more suction runs good for a min. again then same thing happens

Re: strange problem

thanks, i'll do that. might as well give it a shot