I haven't tried the 28's because they are also labbed from Mercury. I always suspected that the lack of cupping would just slip too much. Since I have them, there is no harm in trying them.

I have also ordered a pair of 30's from HoustonProp. He is going to cut the diameter slightly to increase the RPM's on the 30's

that's a start. let us know what happens.

Treadwell

Well, I ran with the 28's this weekend and I believe that they are too small after all. I got them up to 5200 RPMs with a full tank of gas and a crew of 3 and I still had an inch or so of throttle left. To be honest, even if 5200 was maxed out on throttles, that's too close to the 5400 RPM limiters for comfort anyway. If I break loose once or twice, I could be at those limiters way too fast.

The interesting (although not surprising) thing is that once I got to 5000RPMs, I got all the way to 5lbs of boost. The extra boost (remeber that I only had 4 lbs before) could also account for the additional RPMs.

My guess is that the 30's that Darrin is making for me should do the trick. He is going to cut the diameter down slightly in order to gain the missing 300 RPMs. If I can get the 30's to spin to 5200, which should give me the full 5lbs of boost, I should be right on target for 83 - 85 MPH.

BTW, at 5200 RPM,s the 28's ran 79.3 MPM GPS.