2001 Yamaha 25hp bogging down

At the end of last season, my fishing buddy has a 2001 Yamaha 4stroke 25 hp that started bogging down and losing power at high speed (under load) but would come back up if the fuel line bulb would be squeezed every 30 seconds or so. During the winter he replaced the fuel filter, added a fuel water separator, got a new fuel tank and lines, and cleaned and rebuilt the carb. It was still bogging at high speeds so this spring he put in a new fuel pump.
It ran well for the first dozen trips this year but just started acting up in the old fashion again. He changed the fuel water separator but it still isn't right.
Our latest thought is that the carb float is stuck.
What are we missing?
Thanks,
Seb

Re: 2001 Yamaha 25hp bogging down

Does squeezing the bulb still allow it to run on when it starts bogging? I know nothing about 4 stroke marine, but this sounds like it could be something like accelerator pump (if it has one) since you've replaced the fuel pump twice. The other thing I'd say check is the line, but he replaced that too. I'm wondering if the carb still has gunk in the main or high speed jet, or if the port that lets gas into the float bowl has some gunk in it that is keeping gas from coming in? Can you take carb off, float bowl off, and hook up a gas line and see if adequate gas is coming in to fill the bowl. Maybe some of the more experienced guys can comment?