14' with a 50 should be fine. Nothing says you have to have the throttle pinned at all times.
For the motor, corrosion shouldn't be much of an issue. Stainless bolts, slathered with an anti-corrosion compound, then sealed up with marine caulk will be fine.
Do you have any pics of the deck from the top down? I notice the area where the anchor locker would be looks to be fiberglass. Odd that, if the deck is aluminum, the locker wouldn't be as well.
Any inspection hatches or wiring raceways (assuming either exist) should let you peek into the bilge and see what construction is like. I'd assume the hull was laid down, a network of stringers welded or riveted vertically, and the floor on top, again welded or riveted (welded is a lot stronger, but harder to take apart should the need arise.)
As far as needing hydrofoils, you'd need to run the boat to see if there's a need or not.