When I bought my used DSI over a year ago, it came with a Nissan 5hp outboard. The previous owner had sailed it in the Columbia River near Portland, and needed to contend with strong river currents.
I found it a pain in butt to use - heavy, and it really got in the way of the mainsheet traveler system when it was hoisted up out of the water.
I found a friend who wanted to trade his smaller outboard for something beefier for his West Wight Potter 19. I got a Tanaka 3hp outboard which is MUCH smaller and lighter. Here's a pic of both of them side by side:

It's just long enough to get in the water. Ideally I'd put it on a lever motor mount, get it down another 6" so it stays in when I go forward in the boat.
This small motor, not being made anymore but fairly easy to find on eBay or Craigslist, is air-cooled. It's essentially a small chainsaw engine. It can be loud, but it's surprisingly powerful, more so than the electric ones I've seen.
Carlos