HP is HP whether from a 2 stroke or 4 stroke. I'd have thought they would rate it by weight, as 4 strokes are a bit heavy than the 2 strokes.
What's behind the mount - what kind/size backing plate? If that's good, and your wooden mounting board is strong, and the mount itself is sturdy metal, I'd think you'd be o.k. You'd want to have a better lift mechanism, and make sure it locks down so the motor doesn't buck up, especially in reverse.