How much will my boat sink if i add a jackplate

[killerpirate]

Hi! Coming weeks i will be upgrading my boat from a 115hp Merc 4 cyl to a 150HP V6 Merc. Both 2 stroke.
Also, i am adding a 6 inch jackplate on the rear (this weighs 30kg / 66lbs)
My 115 weighs about 154kg / 340lbs (?). The 150 weighs about 184 kg / 406lbs.

Now i am wondering, how far will my transom sink into the water after i add this weight? Ore more someone experienced could give me an indication of how far the mentioned amount of weight will push a boat down?
Boat is a Fletcher 16 arrowsport, about 1.8meters wide (6 feet) and has a deep V.
I once stood on the rear of the boat with a buddy (me 70kg / 150lbs) and my buddy (100kg / 220lbs) and that was on the edge of fine. No water entered the splashwell yet.

Here is my boat