They were rated peak HP at 5500, with an RPM of 6000. I've been playing with props too. The prop diameter is 11.5", the shaft diameter is 13/16, pin drive.
Michigan Wheel #'s that work:
PS 70 = 14 pitch
PS 71 = 12 pitch
PS 72 = 13 pitch
PS 73 = 11 pitch
PS 74 = 10 pitch
PS 75 = 9 pitch
I started with a 14 pitch, but with 4 people in the boat, I couldn't even get on plane... it's only a 14' boat.
With the 12 pitch, and 3 people, it cruises wot at 5600 rpm, with just two and just me, and smooth water, it will hit 5800 rpm. This is what I'm running now, and is a good all around combo. But there isn't enough hole shot to get me up on a single ski, so I have an 11 pitch on it's way.
I also figured out a good way to set the timing... essentially ignore the book, go out on the water with the cover off, loosen the clamp that holds the distributor housing, loosen the two bolts that hold the housing to the head. Have someone pilot the boat at wot, while you rotate the distributor housing to find the maximum rpm. If the rpm drops, you went the wrong way, or went too far.
When I found that sweet spot, it was also good for several hundred rpm, and I had to back off the idle some.
Dave