Hi Beradon,
Just for personal information, why not trailer the boat to a truck weigh station. Ask if you could get the boat (while on the trailer, with full fuel, etc.) weighed. You could then use the factory specs of hull weight + engine weight + full tank of fuel (a bit over 6lbs per gallon) + trailer and see if you are within the weigh station weight. (say that three times fast)
The engine should be mounted so that the anti-cavitation plate is in alignment with the bottom of the boat.
Do you trim up the engine at WOT?