Are their any 3-blade props that will work (recommended) with a YS91? I am scratch building a Ultimate Bipe that I would like to use a 3-blade on but not at the risk of damaging the engine or sacrificing reliability/performance.

14x8 three blade should work well. Try to keep the rpm about 9000 for best results.

Thanks Dave, have you found any brand that works better for 3-balde props in this size?

Try the Graupner, I've heard good reports.

I use a graupner 14x7 3blade and get around 8900 revs. I tried a master airscrew 14x7 and was almost 1000 rpm higher as I remember. the combo I use idles perfectly and is dead reliable.
good luck
Paul

Thanks guys. dragoon, I would like to ask you a couple of questions then,
What aircraft are you flying the 3-blade on and how would you compare it flying with a 2-blade?
Does the 3-blade slow the plane back when throttling back? I also fly full-scaled and it does there.
What is the weight of you plane with the 3-blade?
Thanks much.

Great Planes Stuka, 9 pounds. I have never flown it with a two blade as I wanted the thrust and braking effect that you mentioned, it has an effect on speed when I put it into a dive and flies slowly and scale. The big blades on the graupner 3 blade are different to a MA 2 blade which I fly a lot of my other smaller planes on, mostlt in the above mentioned areas.
Good Luck
Paul