trim and fuel gauge question

Had an opportunity to take the boat out today and I noticed on one run that the trim guage seemed to "bounce around". Upon slowing down, the guage returned to the correct position. Also, on my final run, at WOT my fuel guage started reading flat empty. When I came off the throttle, it returned to the appropriate level which was about 1/3 tank. Any ideas of what may have caused this?

Thanks.

cant say about the trim gauge, but when my fuel tank is near or below 1/4 tank it does the same thing 08 20x2