One other thing to think about is the Jabiru 5100 makes its peak power
at 3300 rpms.

the numbers say @ 2700 rpms, with a 76" dia prop the Motor will be making
somewhere in the low 140 HP range.


According to Jabiru:

Power Rating
170 hp @ 2700 rpm continuous, 180 hp @ 3000 rpm intermittent

http://www.jabiru.net.au/8%20cylinderbodyFrame-1.htm