On the Oday 23 (and on the 22 and 25), the mainsheet does indeed attach to the back stay. That is the way it was designed. Not ideal for sure, but the chainplate was made to handle the loads. And I agree, a traveller would be a nice addition. A few years ago, I became determined to add one to my Oday 23 (same model as yours). I scoured the internet and the docks for ideas. I conferred with hardware reps at boat shows. I spoke with a sailmaker and a stainless fabricator. Here is what I decided: its not worth it. It is very difficult to find a solution that works; the most obvious choices are precluded by the tiller head and the location of the backstay. I seem to remember that someone posted a picture on this website of a traveller that they had made and installed on an Oday 23; I think it was some type of bar that spanned the tiller head. However, because of the location of the backstay, the traveller track had to be pretty short. I don't know how effective it was. I think I concluded that the only way to put in a real traveller was to mount it across the seats in the middle of the cockpit and to change to mid-boom sheeting, both ideas that I really disliked. And after discussing things with my sailmaker, I figured that lack of a traveller could be mostly compensated for with the addition of a good boom vang. So I added a Garhauer vang, and have never regretted my decision. Now, your individual calculation of costs/benefits/aggravation/sailing quality may differ from mine; what works for me might be abhorrent to you. And I agree with Mormandeus: the C22 traveller is a great design; however, I think it only works because it is designed and built into the C22 push pit, and the backstay is designed so it is out of the way. This solution does not easily lend itself to the Oday 23.
For your other issue, I think your 9.9 is bigger than necessary. I have an 8 hp (two stroke) on my Oday 23, and it has plenty of power. My guess is that the prior owner chose that engine because he wanted electric start and a long shaft model. Unfortunately, some manufacturers do not offer those features together on their smallest engines.; I wouldn't be surprised if that is the smallest engine from Honda that combines those feature. If the weight of the engine isn't otherwise causing a problem, then I wouldn't worry about it; consider it the price you pay to save your arm strength from all those pull starts. I know my Admiral considers the electric start to be a real safety feature; she wants to know that she can start the engine in an emergency if she has to.
Oh, and great boat selection! You are going to have a blast. Welcome to the club!
