hmmm...being a used aircraft certainly doesn't help narrow down the problem. It came with 2 probs which match the pictures of the prop used on the hobbico website, so I'm pretty positive I have the correct prop. I've applied pressure from all angles while the motor is running propless, but it doesn't cut out, so it doesn't appear to be a problem with torque. One crazy longshot theory I had...it was raining last night and I was wondering if the prop was washing humid air(not rain) into the engine which was keeping it from running. I'm gonna mount the prop backwards and see what happens. I will keep all your ideas in mind and go fiddle with it some more tonight. We'll see how it goes. Thanks again for the help.