just a thought....
some of the props designed for bravos were designed with the torque of a big block in mind. definitely consult a merc prop application guide and look at some of the ourboard props (the idea being, matching the style of boat, rather than just the motor/drive). lasers or revolutions, or a mid range vengance or tempest may work well. some of the props originally designed for outboards may ease your mind with the drive breakage issues (good lift and holding, durrable,less torque, but you might not see absolute top speed) you might even try a plain set of QS 21'. i had them on a similar set up that ran up around 5100 rpm.....good luck...