Start engine without propeller installed

Yes I have. I didn't do it for very long. The engine gets hot quite quickly, it is very easy to over-rev it and it misfires due to the lack of load. Just be careful with the throttle, it will rev up very quickly.

Not the best thing to do. Can you put it on a stand?

https://www.youtube.com/watch?v=nH1ZpvtXPIA

Thanks all, looks like with care it is possible, I just have to decide if it's better to wait. I was going to try to  start the engine for the first time in 5 years & tune the idle mixture to be close to running smooth. Hard to do the mixture with prop spinning. I have a Rotec TBI installed instead of the 2 carbs.

Do not attempt to run the engine without a propeller as it will take half a second to over-rev and send the valve train into twilight which will result in your pistons impacting your valves.

100% not worth the risk!

The Rotax installation manual states the following:

Never operate the engine without a propeller as this results in serious engine damage from overspeeding. Never fit the propeller directly on the crankshaft.

https://www.rotax-owner.com/pdf/IM_912_Series_Ed3_R0.pdf