why raise deck floor?

[uncleboo]

Assuming you're talking about an outboard boat, most everyone is repowering with 4 strokes or hanging a bracket on them. Either way you are shifting the center of gravity rearward which lowers the stern closer to or below the waterline allowing water in. Raise the decks and scuppers and you have dry feet. These boats were designed for light 2 stroke outboards.
Can't think of anyone maintaining original power, i/o, inboard, outboard that would need to do so.