most 12' aluminum boats have a 350-400 pound capacity weight limit. 500# of people, 67# of motor and a minimum of 30# of fuel and your significantly over the weight limit of the boat.
I have a 12' aluminum boat with s 67 9.8 mercury on it!!
i weigh 175 , a three gallon can and I get 21mph on my speed app.
with me and my wife at approximately 350 lbs total it will go 16.
unless your boat is much heavier construction I think you should do better than 6??
