Thanks Dar. Good to point that out. Very true. However the reason for that RPM in this case, is that particular prop ends up being too small for the 76L. The port timing, and phyical constrains of the engine design do not allow for enough mass-flow for high rpm. Engine was designed for lower rpm use actually using these constraints and packaging to their advantage, resulting in an engine which is most happy turning between 9000 and 12000 rpm peak. The 14x4 and 14x6 are prefered props.

For the 12.25x3.75 the SJ-60L "hover engine" is the best choice. Same size as the .46 and .50. It typically turns that 12.25 prop up much closer to 14,500, but I prefer a std 12x4 myself. It's configured specifically with the lite-muffler and with a different carb to improve fuel flow and provide outstanding throttle response under 3D and hover conditions (better low-rpm and midrange). A standard SJ-50 with std carb and muffler will turn this prop over 15K rpm... but at the scacrifice of a bit of midrange (ends up a tad to rich at mid throttle) and transition qualities which makes it a bit undesireable for fun-fly/3D type stuff. (Anyone interested in the specs of the SJ-60L-Hover is welcome to pm and I can provide them).

I hope this is helpful
Bob