I was tuning my engine (Tiger GP-42) and at WOT the propellar spun off. The engine kept going for about 3 seconds before I was able to cut it. Is there a good chance of damage due to over-revving? Sorry, I'm not familar with these 2 stroke motors.

It should be O.K. Make sure your prop nut is snug. You did`nt by chance have it running in reverse ?

No.
No Chance.

No, I don't think so. I was starting it counter-clock wise and the tail was lifting up at full throttle with the front landing gear blocked so I think it was rotating in the correct direction. Thanks for the help guys.

I thought I torqued the nut down pretty damn good. Should I use some locktite or just torque it down more?

My opinion just torque it down more. I would not use locktite.

Tighten the nut. Walk away for a few minutes and tighten the nut again. I find this particularly usefull with Master Airscrew props as they seem to compress more than the APC ones.

Do NOT use locktite under any circumstances on a prop nut.

Wood props compress easily and need re-tightening. I've never had that problem with MAS or APC props. Just don't use a 4-way "cross" wrench. Get yourself an 8 inch long box wrench of the correct size and you will be able to actually get them tight. Don't worry about damaging the crank or the prop nut by over-tightening it, you're NOT strong enough. No, that's not a challenge or an insult.

I've had a wood prop come loose while hand starting because the wood had compressed slightly but if the engine had fired then that tries to tighten the nut. Any time an engine is running properly it's trying to keep the nut tight on every firing impulse so to have one come loose and throw the prop means something is wrong (unless you've got a reverse rotation engine ). A 2 stroke usually won't backfire like a 4 stroke does to kick it loose but if you're using too much nitro or too hot a plug then the ignition is too far advanced and this can loosen the nut.