Thank you Arcen!
I want to tell you that when i bought my engine, the dealer told me that the apropiated propellers for this engine was 13x7 to 13x9. That is why I´m using it. But when I started flying, I realized that this wasn´t the right choice.
I will try with a 15x8, with the 3253 muffler.
See you!
Ernesto.