Need some guidance...not up to speed on motor performance

Okay...here's what I have.

Alweld 1552
2015 Tohatsu 20 HP 4 stroke
Total weight guestimation is about 750-850lbs

I had a low running motor even though I have a long shaft and 20" transom. The vent plate sat about 2.25" below the bottom of the hull. Well Just installed a mini-jacker jack plate on it. Before I was getting around 21 MPH but I was in the break-in period and not going 100%. Motor ran solid, just lots of spray from the plate being low. Fast forward to this morning, I ran an initial test with the plate installed. Motor could still stand to go up a hair I think, but I am happy with it if I can figure my issue out. Anti-vent plate is still slightly submerged, but I'd rather stay on the safe side. Hole shot is superb and it climbs out of the water like a champ. However, I either have a slippage issue or I might need to reprop and I can't figure out which. I have a mini-tach, which reads off(idle is around 3K), but it's good for seeing RPM changes. Well, now, I hit the same speed, maybe gained a MPH or two, but anything above 3/4 throttle and the RPM sounds like it's hitting the limiter. From 3/4 throttle on, RPM hits about 9200(there again, it's off) and stays there from 3/4 to 100%. Motor also sounds like it's hitting on the limiter as you can hear that slight RPM wavering sound even though it's humming pretty strong. There again, the prop is fully submerged, but I can't figure out where the issue is. I can back off to the 3/4 throttle, even maybe slightly below and hold the same speed. What do you guys think? Is 22 MPH about the max on a stock propped 20 HP outboard? Too much slippage? I am not very experienced or knowledgeable when it comes to this stuff.

Here's what info I do have

Gear ratio: 2.15:1
Speed: 22 MPH(approx)
Max RPM range: 5400-6100 so I assume the limiter is somewhere around the top max listed?
Prop: Not sure what the default prop is for sure, but I have seen posts on the net saying they are a 9 pitch?

I'm not a motor guy, but will chime in and say your speed sounds about right for that setup.

Welcome to the forum!
First off......go into your settings on the Tiny Tach and set it up for your 4-stroke. It has a myriad of settings on it. If you do not know how then go to the website and download the instructions. Pretty simple.
As far as hitting the limiter goes, yes it sounds like you are but you have the tools necessary to tell you that. If that is the case then you have some speed left in the set up.
Second, am betting you have a smart phone. Download a speedometer and use it or a GPS.
Not a single number you mentioned will be usable for anyone here to base a recommendation on. At this point you are saying you do not know the RPM and you do not know the speed and want to know if it is set up right......

Knowing the speed is not the issue, I've done that with both an iPhone and my HB fish finder. Both are showing the same. It may very well be the case, just having a hard time believing that the tohatsu props those motors to cap out at only 22-23 MPH. That's what kind of making me wonder about the situation, but it may very well be the case. If someone else has the same setup, motor wise, and can confirm that it maxes out around that speed, it would help me feel a bit more confident about it.

As for the mini tach, it is the Hardline model. i have a email off to Hardline asking for assistance, but I have tried all the settings on there and that's the lowest idle I see. With the other two, they are both showing over 7K. Tried chaning wire placement, all that good stuff, no change. There again, I can't see true RPM, but I can see changes.