I replaced the outboard on my B27 last fall. I had an old 2 stroke Evinrude 9.9 HP longshaft. I couldn't get it to run consistently and it left me in some very bad situations. I ended up replacing it with a new 4 stroke Nissan 5 HP long shaft. Cost me $1100 at BoatUS. Some feel that's not enough power for the boat, but it moves me along just fine (4 knots @ half throttle in calm water). Folks warned me it wouldn't be enough in bad weather, and that's partly true, I suppose. During last years Good Old Boat regatta, I kept up with the Triton fleet (A4s) heading out to the start line into a 20 kt headwind. Next day, though, near my own marina after a somewhat scary 25 mile sail, I couldn't make more than a knot or so into 35-40 kt winds under the motor alone and had to motorsail.

I went with the smaller motor because I wanted a 4 stroke but wanted to keep the weight down in the lazarette (B27s tend to squat with two much weight back there). I think its a fair compromise for the low price, excellent fuel economy, quiet operation, and through prop exhaust (no more stinky cockpit and can leave the lazarette hatch down). I figure lots of people have gone around the world without any motor at all, so I should be OK on the Chesapeake with something less than the recommended 10 HP.

Soooo, the point of that long diatribe is that the 4 stroke 5 HP Nissan is a good motor at a good price, and would probably do just fine on your Ariel.