I have an OS 40 LA motor on my Sig Kadet LT-40. I have been using an 11x5 prop. When I was at the flying field last week, someone gave me a 12 1/4 x 3 3/4 prop. It seemed to give the motor more power. Is it OK to use this prop on this engine? It does not show up in the recommended list for the motor. Will using it cause an damage to the motor?