this is totally a guess on my part but I would try a 15 pitch aluminum prop - i would think you need something low to move it efficiently. You want to make sure your rpm doesn't go beyond 4800 at full throttle. You would want something that puts you around 4600-4800 at full throttle.
Not having a prop is an issue but were going to need a bit more info. The drive ratio is also necessary and how you plan to use a load the boat. In the thread below on post 7 a guy has the same setup which came with a 15x15.5 from the factory. Being a 4000ft your probably going to need to reduce pitch a couple. If the boat came from the high altitude area then this could be a plus.
This will just get you a ball park to start. Best thing is to find a prop shop or dealer which will let you try a few out. Your WOT should reach 4400 to 4800 rpm.
Ayuh,.... Welcome Aboard,..... The 3.0l should already have the lowest gear ratio of 2:1, 'n I believe the 15" pitch is the smallest pitch you can get for an Alpha drive,....
