I have a 2000 Crownline CR with a 5.7 merc engine. When i engauge the throttle the engine takes several seconds to reach full power.
Now you dont say if you have EFI/MPI or carbs, or a dirtributor or a computer this info we need to know, also what would help is approx weight of the boat, pitch of the props and anything else funny it might be doing,that will help us more to steer you in a direction that would help :-)
What Myles said.
Also, do you mean the tachometer doesnt show full power or the boat feels sluggish getting out of the hole?
More info please.