So I'm currently running 5 blade 28s no idea if the are lab or not . Hit 82 at 5100 rpm . But only did it for a second as I bought the boat long over do for top end refresh, and didn't want disasters. So babied the boat all season, and had refresh done in October/November. Now I'm ready to wind it up !!! Have 525' and ITS/XR
What's the right prop for Mph , 4 blade 30 - 31 ? 29pitch 5 blade . 5 blades are a lot of dough

First thing to do is run it. Your top speed was pretty close to what it should be. You might see 84-85 on a really good day. You can spin your engines to 5300 rpms without an issue. Just saying 5 blades and 4 blades does not mean a lot with out the make of prop.
Top speed of 353

Yes , definitely need to run it. Thanks for the link to the other article lot's of good info!!!

5 blades put more stress on the drive so if you change Id stick with 4

We ran 32P Bravo1 4 blade labbed by BBlades. Found that they were the best overall....Topspeed and cruise was good. The cruise with the 5 blades was certainly a bit better (lower RPM) but as mentioned they are hard on the drives. Good luck...If I can ever be of assistance feel free to reach out. Enjoy the season and stay safe.

Local guy running 525's/5 blades was snapping drives - but 5 were faster than 4 blades. 4 was his choice

I don't have 525s, but I think power and speed is similar. I'd like to make a couple points.

1. I ran 5 blade 29 pitch for 110 hours. ITS XR, no issues and gear lube looks good when I change it. My best mph on those was over 84mph with a normal load, but that was 65 degree air. I'd get loaded down full of fuel, water, coolers, people and it was 78mph on a 90 degree day. I'd work like hell to see 79.9mph on those days and it ate me alive. I'd see 5000 rpm like that maybe.
2. That same day I put 30p Merc labbed 4 blade bravos on and I picked up rpm and speed...not a ton. 85-86mph. The difference is that on a 90 degree day loaded with all my buddies and all of our stuff its easy to see 83mph any time I want in any conditions. I don't have to work for it I just pin the throttle and steer the boat. Glass smooth water in Tennesse or the roughest day of the shootout at LOTO I'm going 83 no matter what people are in the boat.
3. Boat slips more coming up on plane...I can feel it. Pops up quicker honestly.

The downside.....
1. Yes I lost cruising speed and probably some acceleration going to the Bravos. I don't count gas money so I don't care. I just turn more rpm and cruise everywhere at 65-70 anyway. I wish I was on the water enough to care about gas.
2. The labbed props aren't equal. They are different so I see 5400 rpm on one engine and 5570 on the other. That drives me nuts so I just change the screen LOL. In hindsight I should have just got the standard non-lab props I think and it would be more ideal for rpm to be 5400.

I ran 28 Maximus 15.25 diameter with the diffuser and fully labbed. Low to mid 80s is where your going to land. 05 353 525 XR/ITS

What lowers are you running?

Drive ratio?