Sorry Beerbelly, convention on here is kts so I presumed that's what you were talking.
If you were getting 14 or less on the Aerotec with a 15 then as Fenlander says something was wrong!
David, my (your) old Fastroller 340 with a 9.8 did as well as the Aerotec with a 15.
I did set up my 15 with a tiny tach but it's kaput now. At the time I think we were at 5400 or similar but I'd need to check that. Engine runs great, prop is near mint, pops up on plane. Is there anything else to suspect if it's down on power? Would it still reach max/normal revs at WOT?