Hi Dave, i have one of these. Is a great engine. The 23 likes small load props, for RC the ticket is a 9X4 and for fast ships(smaller) an 8X6 will go fine. Idle is superb. Fuel must be all castor oil. If you use nitro maintain the limit to 5%. Power is great and also the fuel consuption is high for a small engine, but at least is very powerful. The compression ratios is high and tends to distort plug elements easily. a 9X6 prop overheat it in my using and run erratically. The carb is firts class, maybe a little sensitive to set, but once dialed is done. Great small engine friend. In a past trainer i used an old TF 10X3.5 Nylon, also with great results, and in a small pattern bird the 9X4. First class starter with one or two flips and also a fierce finger "biter" heheheheh..... Hope that this help you
cheers