Ive used a bracket rated for 30hp 4-stroke to hold a 40hp 2 stroke for the last few years now with no issues. I can say that the 4stroke brackets are alot stronger than the others, but if your motor falls under the weight limit, i dont see a reason it wouldnt work.
But the problem is, his motor is a Four Stroke, not a Two Stroke. Like someone has already mentioned, weight isn't the only issue. Four Strokes also generally torquier than Two Strokes, and an underrated bracket will fatigue.
As tempting as it is, don't convince yourself it's all a marketing scam in order to save a bit of money. Do it right and you won't have anything to worry about.