First off, great looking intake duct! =D> That design looks like it would be a LOT easier to fit into the hull than the Yamaha OEM pump, with that ridiculous wedge shape along the inside. How thick is the duct? Reason I ask is Yamaha OEM ducts are very thin cast aluminum, and that's the only thing that worries me about running in gravel or oyster shells....having something bust a hole in it. An aftermarket pump intake like this, made of thicker material, would be just the ticket.
As to the impeller, my boat weighs about 1200 lbs fully rigged, and I'm currently running a Solas Concord 14/21. I was previously running a 13/19 Concord. Good results with both of them. The 13/19 was getting about 37 MPH on GPS (those yamaha dream-ometers lie about speed!) This 14/21 is getting about 41 MPH. A couple of weeks ago, me and my girlfriend went to a rock bar in the PeeDee to get rocks for our front yard. We had about 300 lbs of rocks (2 bushel bags almost full) and the 2 of us, so I figure that was at least a 600 lb load. Although it may have been a little slower on takeoff, the boat had no issues carrying that weight.
When I had the 2 stroke engine, I also ran a Solas X prop, in a 14.5/17 pitch. That also got about 40 MPH
Your best bet would be to contact Impros as they specialize in rebuilding impellers, as well as re-pitching them for custom applications. That's what I did. Gave them the specs as far as the size of the boat, and the approximate weight, and they recommended a Solas Concord 14/20, re-pitched to 14/21. I'm thinking that due to your boat's wider beam, it may require a different pitch than what I'm running.
