I removed the drive shower and tried another 26LH B1 that I had. No more cavitation issues. Hooked up good, couln't bow it out or make it slip. Still a little under propped though. Just touching rev limiter at 71MPH.

Thats cool Snapmorgan! Making headway! Im hoping to see low 70's with my new motor! Hey Adv 575, I was looking at an Imco extension box with 3" lift. I measured my x today, bout 6 1/2 " at trim height, ie trim when running. Would this extension box hurt or help??? Would my B1x bolt up? You seem to have the answers to make 28's go fast, looking to tap your knowlage!!

3" raised box, you are going to have to raise the engine. Use standard IMCO box and go with a -3 IMCO SC lower. That will put you on the money. 6 1/2 X is crazy low. Check X with drive at neutral trim. Neutral trim is prop shaft parallel to the bottom of boat. use a yard stick or some type of straight edge. I don't like raising the engine on a 28'. Hull is plenty deep for a nice blower motor. I have a 575 SCI stock in mine. What prop are you using?

Im running a labbed 24p bravo now. Saw 56 max on gps at 6000' with the 496ho last week. Sold it and picking up a 600+ hp 557 efi motor next week. Sure I will have to prop up at lower elevation but could only turn it 4400 at 6. Just wanting to start gathering parts for future outdrive upgrades. You think a sc lower will hold up for a while on that b1x with no hard hole shots? Was thinking like you said, ext box & lower to start with, maybe some steering soon, then the scx upper later.

Thor your elevation defiantly plays against your speed quests. Example, my 575 SCI with inner cooler which is approximately 650 HP, I use a 28 4-blade labbed a bit. SC will hold up if your're smart on the hole shot. I do run SCX's on my 34. But my 28' I have a XR with the 4- blade. With your elevation, consider a blower. Elevation makes a blower even more sensible. IMO stay clear of 5-blade props on 28. The already have natural stern lift. Your're on target with the box. Raise the drive and move the prop back. She'll slip a little down low but will fly on the top.
Also, HYD steering is a must first improvement. Period!!

Top speed
 

27 victory 454 mag with procharger 5psi boost runs 74 mph in chop !!

Wow, I'd have thought with the HP you guys are running, your boats would be faster. I have always thought my 32 Victory was a fat beotch, but with just a couple 496HOs, I have GPSd 81. I do know the triple steps like a little more chop though. Nowhere near the fastest, but respectable with stock power I think.

32 Victory in IMO has the best hull for speed. Even it needs some healthy power to get it to 100 MPH. My 34 has a good hull, but it's quite tall compared to a 32'

My 27 was set up exactly the same. I have a -2 shorty and its still right around 4-4.5" below the keel. The -2 helped pick up a few mph. Advantage sets up their boats for 496s so itll get on plane easy and pull skiiers and tubers at slow speeds, not for us guys trying to go fast.

I would like to do a -3 someday and a box, but then it wouldn't fit in my garage haha. Keep us updated with your project!

Well, Fired up the new motor today,.....Opps, I jizzed in my pants!! Sounds great, every thing is working good, will go out for a water test on Sat. Suposed to get up to 54 deg. I think I,m going to need to buy antifreeze by the 55 gal drum!!! We'll see how she runs, save up some$$$, Going to go with the box, -2, Hydro steering all at once, come spring.