Hi Kilda – welcome to the forum! Another composite boat.
I like the low weight of the Honda and the air cooling appeals to me, in principle anyway. The only part I’m not sure about is the throttle/centrifugal clutch. I’m used to a Yamaha with conventional throttle and separate gear selection (F or N) and often run it at or just above idling speed, which is really quiet and surprisingly fast in low wind speeds (which is when you tend to use your engine). But I know that many W owners use the Honda very successfully, in fact I would say that it’s probably the most common 4-stroke engine amongst the people that I have sailed with, and would be very high on my list if I needed a replacement.
You’ll find quite a lot of discussion of outboards if you search around the forum, and generally I think it’s accepted that 2 to 2.5 hp is about right for a Wayfarer. You shouldn’t need a long shaft. It depends on your bracket too, but the anti-ventilation plate should be level with or just below the bottom of the transom to keep the prop well under water without being too deep.