With a bracket you'll want the lightest motor possible to minimize the rearward shift in CG. I believe the E-Tec is the lightest 250/300 on the market and BRP has built a great reputation with them, so that would a good choice if a high cruise speed is your top priority. The 250 and 300 are the same basic powerhead, but my experience is that a motor NOT tuned for max HP (i.e., the 250) might actually have MORE mid-range torque, which is what you need to climbing up on plane with a heavy load, or running at min planing speed in snotty conditions. Whichever one you pick, it's very important to have a Platinum certified dealer do the initial setup to properly purge the oil lines and check the fuel supply line for leaks and pressure drop using the BRP test kit. Would also suggest checking out this website if you haven't already seen it:
http://www.etecownersgroup.com/post/...e-Shot-6039207 It's the CSC equivalent for E-Tec motors!
Motor height with a bracket can be tricky. In my experience, the old rule of thumb of raising motor 1" for every foot of setback will result in motor mounted too low. You want to be able to see the AV plate above the water when up on plane and trimmed for cruise. Don Herman mounted my 30" bracket at exactly the right height; you want it as low as possible for max flotation, with swim platform just an inch or two above water, which is where mine is. My 25" motor is mounted as high as it can go on the bracket, but AV plate is still under water and needs to come up another inch or so. Am considering adding a spacer plate to allow raising it more. Suggest you discuss bracket and motor mounting heights for the 30" motor with Don.