A friend of mine has a
Cape Dory 30 with a 22 hp engine. It pushes it around just fine.
One day he was going out through a pass in the barrier reef in
Belize. Took him 10 minutes to go a couple of hundred feet. He forgot to dog down his forward
hatch. He watched the
water filling his
boat for 10 long minutes as he could not turn or leave the tiller.
In short heavy seas you need a lot more power and a matching prop. It all depends on where you want to go.