I have a 2000 Obmc heat with a single 750 running an Imco SCX and a Maximus 5b @p28 slipping 18%... I see 81mph at 5500rpm. Used to run 85 with the XR.. my prop shaft is only 2” from
the bottom of the boat now with the Imco drive. Would I find that speed again with a 1-2” spacer. After 70mph it also walks/chimes more than it used too with the xr drive

what’s the XD on your boat?

Centerline of propshaft is roughly 1.5" above bottom of boat. This measurement was done using a level on the bottom of the boat to extend the front of the outdrive. Measurement taken with trim in neutral position parallel with bottom of boat. Neutral trim is my best performance also.

I may have misspoke. I don't believe i actually have cavitation coming onto plane. As i come up onto a plane and the boat is accelerating between 20 and 30 MPH, the prop is transitioning from having all 5 blades in the water to only the lower 1/2 of the blades biting the water. During this transition, there is some add'l slip that goes completely away by 30-35 MPH. I also raise the trim to neutral during the transition between 20 to 35 MPH. i don't believe i have any serious cavitation where a vapor filled cavity is created around the prop. No expert, only an assessment.

does your walk/chime at higher speeds. 75+?

Yes, it's a handful above 75-80. I do NOT have trim tabs and I run the Maximus 5 30p with the diffuser ring still on it (stock config). I've thought about taking off the diffuser ring to reduce transom lift. I would love to hear from other Heat owners that run in the 80's and see what they have done to create more stability.

You're thinking of adding the spacer to drop the prop shaft down so the centerline of the shaft is parallel with the bottom?

With our old engine we run to 87 mph Very easily. No chine, no issues at all. This is spinning a labbed 32p bravo 1 labbed by Merc racing. We have tabs never use them. I do have video of us along side a fountain that is chine walking like crazy. If you want to see the video I can post on you tube. Our heat is
https://cimg7.ibsrv.net/gimg/www.off...f5d072c90.jpeg
Heat on right chap on left, his hers boats
https://cimg9.ibsrv.net/gimg/www.off...5220c4bf0.jpeg
This is our gps track last year with me and my boys running the Colorado with friends. Later that afternoon we ran south again and met up with the fountain.

@Cerberus66
Thanks! Are you in PHX area? Maybe one day and you can show me how to run the Colorado. I just relocated from WA state. Currently boating in NORCAL Delta and Tahoe before towing south next fall.

We go to havasu. Almost every weekend during the warm season. We run from Parker to topock.