Seems to me, and I'm certainly not an expert, that sailboats would make lousy motorboats, with possibly McGregors being excepted. The hull designs are going to be different. Almost any powerboat is going to be at some point on its hull flatter than a sailboat. Conversely, a sailboat's hull will be more rounded. That would make for an uncomfortably rolly ride, especially in any swells.
By the way, I have it both ways. I've sailed for almost 30 years, and I love my fishing. Lost a Santana 20 in Katrina, and my wife and I are on the verge of getting another sailboat (after hurricane season ends). But I love my Whaler and going fishing in the marsh. I think here in South Louisiana, we don't care which way you go, it's being on the water that counts.