Actually the prop chart for an OS 46FX recomends props from a 10.5x6 up to as high as a 12x7. All of the 46FXs I own run 100% better with a 10x6,7,8 than they do with an 11x6,7,8. Sorry.. but I have four with 2-300+ runs between them, on 15% cool power, and they simply run better and yes cooler on the 10" prop. They also have no dead sticks, will easily hand start and run perfectly every time. I have tached them, and an 11x6 runs about the same RPMs as a 10x8 anyway, but the 10x8 will throw more air over the cooling fins allowing for a cooler running engine. Try a 10x7,8(APC) and an OS #3 plug and see if it works.