Just heard back from one of them: 26P Bravo1 4-blades.
It sounds like regardless of what was stamped on the original props (could have been 28s turned down to 26 or so).

...that you need to get a set of known 26P Bravo1 4-blades.

Those props may have been a set that goes with the boat when they wanted to pull a top speed run, and work when the boat has a light load, fuel, passengers, gear, etc. etc. There is a technique the race boat folks use with tall top end props, which involves letting the boat start to pitch the nose up, and waiting until it starts to blow out...
...then yank the throttles back, and let the wake push the boat up on plane; while you throttle up through the wall of water hitting the back of the boat. It's not something you want to do everyday/every time; and it's tricky to master.

I have an 03' 33ZX with 496HOs. The boat came with 26s, but I don't know if they were ever "touched". They had some initials stamped on them, so I think they were. Never had a problem getting on plane, but cruise speed sucked - 3500rpm maybe 42mph. I bought new 28s from Merc (unlabbed). Boat gets on plane the same, cruise up by 10mph (low 50s at 3500), and I only lost about 1-2 mph top end (little over 70, depending on day and fuel). Hope this helps...

Donnie sead he was going to give them a call but in my eyes I don't think they will say ya I took the good props off and put some garbage ones on....lol just my thought process

Cool thanks

See the info "Cignificant" posted above. He is one of the two I mentioned. The other one runs 26s.

Ron, shouldn't he be running 26s with the smaller motors, compared to yours with the 500s? I guess it should still plane with the 28s..... Just switch your props, then you know what you have.

Yup. Chances are you are correct.

Yes I seen that. So it came with 26s and can run with stock 28s so if in deed the 28s that he has have been labed for a particular situation / boat that could definitely throw things way out of whack. Thanks for all the help.

That's the plan for now and would try it now if it wasn't winterized and tucked away in the back of a building next to mine. Spring can't get here soon enough. I just want to get all of the kinks worked out for him so he can be happy about his new boat. He had all new bellows gimbal bearings and pins done. So hopefully he will be good to go

Sounds like it wouldn't be a bad investment for you to both go in on a set of 26P B1 props. They may turn out to be ideal on his boat, or the perfect set of backup/spares for both of you if you guys boat together; especially if you make long runs together. There was a smokin' deal on a set of 26s here a week or so ago, sold immediately. Keep your eyes peeled, as this would not be money wasted.