Hello again to everyone! I have an old but new OS .35 FP. I want to install it on a trainer to put it to good use and I am wondering what size prop should I be using? Thanks for your help.

I'd say anything within 9-10 (length) x 5-7 (pitch) would be OK. Try a 9x6 or a 10x5 to start out.

I could not agree more. A nice 10/4 or 10/5 would work just great. In my vested opioion, the FP seris of engines from OS were the best entry level engines made. Good Luck, Dave

Thanks for your help guys!