RE: Calculations(will it float?)
keeping it simple here, the weight of the boat cannot exceed the weight of water that would fill the volume of the hull. I'm leaving it at that.
Secondly---- cog = center of gravity, the balance point of the boat. fore to aft
third. this is a vague question, many many factors make up how fast a boat goes, from hull design, weight, power, power source, hardware, props. You could figure this out yourself in a few hours on the various boat forums. In general to make a boat go fast you want a moderately shallow vee'd hull, and a power plant that can put out enough power to make it go fast........duh.... Anyway, Let say you're using a 700 series motor, you want it to go fast as possible, you start out with a small prop for safety and work your way up prop sizes till you find the sweet spot, max speed, with the least possible damage to the drivetrain. There obviously are more variable, which you can find in the forums.
I dont mind answering some noob questions, besides lets just say, I wont remember this conversation in the morning so no biggy.