Our club had a Bristol Caravel 22, 2850 lbs displacement
and an Islander Excalbur 26, 3700 lbs displacement. Both had 6 hp motors on them and they had plenty of speed. The times that they couldn't push the boat at a reasonable speed, extra horsepower wouldn't have helped as the prop was out of the water
too much of the time. I'm pretty sure the Bristol originally had a 4 hp, but making all the engines interchangeable won out.
If you had an inboard with the prop way down deep in the water
then putting a large engine
on your boat could be argued as a good thing to do. I don't think a big outboard
setting your boat out of trim to make it sail worse for something that is likely to be useless in big winds and waves a good tradeoff.
Particularly remember trying to leave a marina with the 26 having to turn around back behind the breakwater, get the sails
up and sail out upwind because the engine spending more time screaming in the air than staying in the water.