A few things to keep in mind
When you are buying, keep in mind:Buy the longest shaft model available. Although 20 inches is considered a long shaft model, the propeller will be lifted out of the water in rough (and not so rough) conditions. You won't be sorry for going with the 25 inch model. However, seeing as how most manufacturers don't offer them, and those that do don't offer them on the smaller models, this may not be an option for you.The 9.8 horsepower is more than adequate for the Oday 22. I have an 8 for my 23, and it pushes the boat at hull speed at 3/4 throttle. If you are going with a two stroke, 6 hp will be adequate, 8 more than enough. I just bought a Nissan 8 hp two stroke long shaft w/electric start, and it has been very reliable.If you are thinking of going for a four stroke engine, you can go with an even smaller engine. Four strokes produce more torque at lower rpms. In my experience, a 6 hp four stroke will be roughly equivalent to a an 8 or 9.9 hp two stroke. It will also cost and weigh more. Also critical: if you go with a four stroke, its not just the weight rating that is important; make certain your mounting bracket is specifically rated to carry a four stroke engine. That extra torque will put extra strain on the bracket. You don't want that thing cracking your transom. If the bracket on your boat is original equipment, it probably can't handle a four stroke; there were no four stroke outboards when Oday was in business.