What is the typical slip % on a single engine cat?
I ran mine last Sunday and the slip was 3.8%

112 MPH , Bravo 28 ( used 27 ), 1.36 , 6100 RPM

3.8% is a very good number especially with a high propshaft like you have.

Extraordinary. I'd frame those numbers.

Almost seems too low to believe . Not saying you'd have a reason to lie, what I mean is that it seems like something is wrong in the calculations .
Is the prop stock or modified in any way ?
A stock 28 bravo prop use 27.3 for prop cal. If the prop has had cup added , or the blades trued then use 28
Are you SURE of the RPM? All 4 of my Livorsi tachs are 250-300 lower than actual

If indeed your numbers are correct your slip is 2% . I really don't think that is physically possible

I agree . I also noticed, that tach's aren't always 100% accurate, just like most electrical based gauges. Theres also the question of the GPS speedo accuracy these days. Seems like some are a little more optimistic than others.

I try to watch my chartplotter MPH when running for top speed. Its a little easier on a slower boat like mine I guess. Reason I do though, is I can watch the speedo going along, 83, 84.5, 86, 87.5, and so on, and watch them stabilize. Recall features are cool, but I have seen the GPS numbers spike 2-3, or more mph in a flash, which may not have been the actual number, but the recall shows it was.

The tack is in sync with the EFI computer, The GPS speedo is in sync with the one on my phone, The prop is a bone stock BRAVO 28 and I used 27 in the calculation (the bell is cut off ),The drive is 1.34 or 1.36 ratio.
I have almost no drive in the water. Only the skag is in the water, the water is hitting the underside of the bullet at top speed. I find it hard to believe also.
This boat won't begin to get on plane without the mods I have done to the trim system.

What are the slip #'s on a cat set up for racing???

I don't know what the race teams are running for slip #s, and I would assume that many race teams would not disclose that info. but whatever you have done to achieve these #s is quite impressive! Please keep us up to date on this. I'm sure you know the drive ratio is in either 1.36 or 1.34. I was thinking maybe a 1.25 but then your slip #s would be way high at 10%. whatever you are doing it is working! I would love have double your #s!

The drive was built for me by Mr. Gadgets. ( Dick Tryce.)
When I went from a 1.5 ratio to the new drive ( 1.34 or 1.36 ) I lost 600 RPM and I believe that is normal RPM loss for that change.

Yeah I have met Dick Tryce before. and is a hell of a great guy and drive builder! Like I said those are awesome slip #s.