Most 6HP or less motors are now single cylinder 4 strokes, as a group they tend to be loud and vibrate a great deal, this isn't bad for short runs, but if you want to troll for any length of time it can become rather annoying.

And there is a big difference between the smaller motors and the full sized 8s and 9.9s when it come to available thrust.

The small ones are nice if you don't plan to use it much though.