As posts above. Although I would guess if it's OK at idle then it'sa dynamic problem, so to expand slightly on Will's post-
If you got power trim - once on the plane, trim up slowly until it gets easy to steer or the prop jumps out the water. Once the prop starts letting go, trim back in a touch
Manual trim - Time to get your fingers wet! Move the pin on the clamp (the one the engine sits against when fully down) up one hole at a time. Things will become easier to steer (and will be slightly longer to plane) until you trim it so far up the prop lets go at the first sign of a wave, at which point drop it a hole. You may also find a fuel economy inceaceon cruise if you raise it. Somewhere in the middle is your
I had two settings on my old Suz - One for when I was doing rescue work and had a lot of stop -start (needed to get on the plane quick, and a higher hole for cruising.