I was running a consitant 61. I saw 63 once, but was never able to recreate that. With the procharger I'm running 71 - 74. With the higher HP does your stern ride higher at WOT than it used to?

Can't say I've noticed a difference. But I'm running an ITS with XR drive so the boat handles a little different than other 28's I've driven anyway. I actually think it's a little slower, but that could be just the XR drive. I never saw more than 61 when it was stock. It definitely needs all the bow lift it can get. I tried the hydromotive P5 and it had way too much stern lift and lost about 5 MPH. The P5X has much more bow lift. Seems like adding some cup to the tips helps on this hull too.

Hey steve do you think the x drive will handle 600+hp?

The Xdrive is interesting. It is a good upgrade over the standard B1, although not as stout as the XR. To my knowledge, the biggest motor Merc is putting in front of the X is the 496/425 HO. It will probably hold up if you don't drag race it out of the hole and pound around in rough water. I would also switch to synthetic oil and change it every 25 hours.
If it does break, then you can go ahead and rebuild it with the XR or other aftermarket (like Imco) internals and prop shaft.
Good luck.
Steve

It also accepts XR gears very easily. RV did this on our new one prior to us taking ownership. Of course RV did this because he lost an X gear at cruise on Lake Michigan
Take a peek here for some good info...
http://www.go-fast.com/mercruiser_bravo_sterndrives.htm

welcome aboard .