ORIGINAL: IXLR8
I have this same engine(four of them) and they don't run very well at all with an 11x6 prop(APC) or anything other than an OS# 3, OS #8, or Enya glow plug. An 11x6 is too much prop for it. I also had a friend that always complained about how his ran but he always ran an 11x6 on it with a Fox glow plug. When he finally listened to me and changed to a 10x7 and an OS#3 he was suddenly very pleased with it.
Switch to an APC 10x6,7, or 8 and use a OS#3 glow plug and it will probably run 100% better. Then make sure you have the low end set correctly. Most engines arrive with the low needle on the rich side so you may need to lean it out a bit.
Sorry...but I have several OS46FX's and I don't agree. I run Fox plugs, and an 11x6 prop and it runs great....no deadsticks, immediate start, no need to reset the fuel mixture unless the weather is dramatically different.
I use an 11x6 for slow flight and and 11x8 for quick flight. If you look at the top Flite prop chart or any prop chart for that matter...an 11x6 is the middle recommended prop for a 46-52 sized engine. I use 10x6's on my 40's. The chances of overheating a 46 with a 10x6 seems like it would increase exponential and that engine will be maxed out on revs and runs like a crazy person. I've never tached the 11x6 prop but I can listen to the engine and know its up there...