I was experiencing the same problems last year. It was in the fall, and the leaves on the water were everywhere. I thought that every time i accelerated, leaves were clogging up the intake. After countless attempts to fix the problem, and some help from the forum, I found out that my electronic rev limiter was the culprit. When I gave the engine more than 1/2 throttle, it would bog down and not run. The engine was hitting the rev limiter, causing it to miss fire and not get near the right amount of RPMs. I unplugged the rev limiter, and it ran fine again. Check that out, it may be the problem.
Sidenote: I ordered a new rev limiter, and installed it, only to have the same problem, so it must not be the actual rev limiter, but somewhere in the wiring. I do know that it has something to do with the rev limiter, because I have to run without it plugged in to get my motor to operate correctly. Until I have the time to work on getting it fixed, I have to run carefully and make sure never to run full throttle.