Hmmm...
We have strong tidal currents here, too (6 or so knots being about average). Like Roger, I prefer an electric motor, and I also use the tidal flow to help get me where I want to go when necessary (or else simply wait for the flow to slacken some -- gives me a reasonable window for making distance over the ground). I don't know about a "light 8 hp", unless you're talking short-shaft as opposed to long-shaft. If you must have a combustion engine, you might consider a smaller one in the 5 to 6 hp range -- that'll give you all the power you need, without the greatly excessive weight of an 8 hp. You'll probably still have to trim 'er by the head a little to compensate for the weight of even the smaller (5 - 6 hp) engine. The key to speed through the water in a sailing hull is to keep the rocker high at the stern, to alleviate excessive friction, ie, drag, which slows you down (which is what I was hinting at in my first response). I don't know about the waters in your area, but I've sailed from Chincoteague Island, VA. to Ocean City, MD. (about 30 miles one way, give or take). I've found that since a Daysailer has such a shoal draft, I can largely sail under the shoreline when I need to avoid currents that are running at full bore in the opposite direction I'm heading. I hope this helps -- and again, good luck to you on your upcoming sailing adventures!