Hi,
Towing a boat weighing near to 2.5T should only be considered with a large 4WD.
I have a 6.2 Litre Maloo and I would not even consider towing something of that weight with it. I have plently of power but when it comes to braking, cornering, etc I would not trust it.
Getting the boat up a ramp would be a real concern.
Only way to go is large 4WD and you will not be disappointed and should not have too many dramas. Going to anything smaller and you will only be asking for troubles.
My 2 bobs worth anyway.