Re: outboard size for 23-26' boats?
I can only speak from my own experience. I had a Coronado 25, at about 4,500 lbs. Started with a 6HP which was OK in calm water. However, San Francisco Bay is anything but calm with strong currents. Long story short, went to a 15HP, same size and weight as the 9.9HP. It was all the power I needed, probably the 9.9 would have been enough.
Suggest you get plenty of power with the longest shaft that will fit. There may be quite a bit of weight and wind-age difference between a 23 and 26 foot boat.