APC has an 18.1-11 available as well as a new 18.1-12. I ran the 11 all last year and is very quiet along with some changes for the better in flight performance and feel compared to the 18.1-10. I am currently evaluating the 12 pitch. The engine has plenty of power to turn this prop also. I requested the blade be narrowed slightly so the engine would not load on the uplines since the pitch was increased. Only have 4 flights on the prop so more testing is needed before I can say for sure. Running a YS 170.

Bill Cunningham