Dave ... I got an older version YS61 long stroke. I am thinking of using her in Balsa USA Enforcer. What prop might be good for this engine? Thanks.

11x10, 11x11,11x12, 12x8,12x9, 13x6,13x7. Lots of choices.

Thanks a lot! those are huge props!!! Is the engine that good? Hehehe ... I am a happy bunny!!!

Yes it is !

I run YS 61LS with Hatori 650. My favorite was 12x11 running 10600, 10 % nitro. Relatively quiet, too.
A slightly smaller prop like 11x10 will let it turn more and give more power also but will also increase noise.

ini

Great!

Dave ... am keen on using the YS61 for the Balsa USA Enforcer ... what pusher prop would you recommend? Thanks!!!

I don't have a clue, really. Get something in the same size range as the tractor props and try it.