Ray Most of the reason builders do not run the engine without a prop is because it is too easy to over rev the engine with no resistance at all, and because it is a little like dry firing a bow; you develop all this energy with no where to go, so it turns in on itself with sometimes disastrous consequences. Without the prop your temp will climb very quickly as well as, and if you do not run it long enough to let oil circulate real well, then all your startup lube and pre-oil you applied during assembly will be gone, without being replaced by fresh oil. Not what you want to hear, but I would wait and run the engine with prop, so that you can follow initial run in and break in recommendations based on your engine maker/builder.
Colin N96TA
