Typically, a 2:1 power-to-weight ratio is desireable for unlimited imac and 3D, but a 1.5:1 ratio stil ain't bad. If you are not running a pipe on that engine, though, you can expect degraded climbout performance, as 2-strokes are lacking in torque, especially without a pipe, and quickly excellerating that prop from hover throttle to full throttle is hard to do.
BTW, you may want to try a 17X8 or 17X6 to get more brute pulling power. It will also help to keep your downline speed in imac more consistant.