RE: Magnum/ASP 108
Jim,
I am sorry to disappoint you, but according to the [link=http://www.mvvs.nl/prop-power-calculator.xls]PropPower calculator[/link], the output your new engine is showing is barely 1.156 HP at this RPM...
Just to give you a comparison point, and OS.46AX, spinning an APC 10x6 at 14,300 RPM, on 15% nitro (that is what various tests clocked it at), is putting out an actual 1.144 HP.
Check to find what is wrong; as this much larger engine should be showing much, much more power.
It really does not matter if the power is 'sufficient' for your needs. It's still very low for this engine.