Gentlemen, I have a newly restored Fly Baby but don't know what prop I should be using. The Fly Baby had a C-65 on it years ago. It developed problems and did not fly for several years. The engine was sold. I purchased the Fly Baby and a used C-85 and a used prop. Put it all together and have been flying it. But the engine over-rev's easily. I feel that the prop is too small for this engine. It jumps off the ground and climbs out great. But once you level off, you really have to think about not giving it too much throttle because it will over-rev. I am wondering if anyone can recommend a proper prop size for a Fly Baby using a C-85? You can see details of my fly baby at www.PTA-Online.com if you like. Thanks in advance for your help, Mark Millerborg Owner Planes, Trains, & Automobiles The BEST Little Hobby Shop in Texas! www.PTA-Online.com