Yamaha 75 problem

[fishcamp01]

While running around 4,000 rpm, my 1998 75 Yamaha suddenly began losing rpms and went down to idle with the throttle still open. I let it idle for a few seconds and them it ran fine for another few minutes and the episode would repeat. It got to where I could throttle down as soon as I heard the rpm's drop and then throttle back up maintaining plane. It was not sputtering as if it was misfiring, it was a smooth rapid decent of rpm's. I just had the carbs cleaned and adjusted and the plugs seem fine. I would think if it were some kind of fuel line clog, it would not throttle right back up.