Tested the tech on my friends engines, and on the MDS 40 it reads 12000 and his 0s 40 la reads 12500. The tech it set for 2 blade, I'm using a 2 blade. Then put back the Rossies and it said the same thing 25000 to 25500RPM's steady (screaming very loud) This engine is not much bigger then a 40 size.