I've got an 06 2665, I do have the same problem. I have to go tabs full down, and nail the throttle, it will take some time, but will eventually come up on plane. With 5-6 adults on, I ask people to move forward, which helps.
I don't know where your water is coming from, but I know when I bought mine last spring, there was a bunch (30-40 gallons estimated) of water in the bilge under the mid-berth. There is an access hatch there, and it was just full of water. It turns out that the shower/galley sump pump wasn't hooked up properly, so the water wasn't getting pumped out to the holding tank. I'm pretty sure that there are passage ways from the cabin bilge back to the engine room, I wonder if you might have the same problem, and when you go bow high to get on plane, the water goes back through those passage ways? Might be worth a look.
2006 2665 Commodore - Mercruiser 6.2L - Bravo III