Is this a sea craft?

[KenB]

How much floatation do you have to add to get a sea craft to float? Figure 500 lbs for motor and steering, etc. The rest of a 20 is 1500 lbs?

So 2000 lbs of floatation. 60 lbs per cubic foot float... need 30 feet of floatation. The stringers are like 12' x 1' x 6" x 2 stringers = 25 cubic feet.
SO another 6 cubic feet is what, the space outboard of the stringers? The whaler nerds can go suck on that egg.

Foam numbers from here: http://www.shopmaninc.com/foam.html

ALso, does a floatation bracket and closed transom solve the problem? From the video it sounds like they were taking on water, gunned the engine, and the transom swamped as the water moved to the back of the boat.