Then haul the boat, remove the brass inner hull drain plug and drain it. Unless the bottom is dirty with growth, 5 mph loss of speed is like having 3 extra people in the boat. Your stainless prop should have adequate cup to pick up the bow under normal conditions. Something is wrong and water may be the issue. Check and see if the rear livewells are draining properly when you run and not plugged with moss or barnacles. The holes are only a 1/4-5/16 inch in diameter. This may not cause the bow to drop but could kill top end if your are hauling around 15 gallons of water that can`t escape through the normal overflow drain system.
Agree, water/growth are possible issues, as Fitz suggested. Not a pretty topic, but you may have waterlogged stringers.Here's a thought. Check here on the board the dry hull weight as manufactured, add the engine weight, fuel weight, batt/ trailer weight, etc, then take her to some truck scales. You should get a fairly accurate idea. Pretty close, or not so close. Best, and keep us posted. gran