I probably would not run it below 900-1000 rpm for long distance cruising, especially if engines are not yet broken in. If not broken in, I'd run as much as you can around 2000-2200 and get the rings seated in.
If already broken in, 1000rpm is fine, but a couple times a day run it up to 2200 for maybe ten minutes.
That boat has A LOT of hp for it's size.