Running a 312 Formula Fastech bravo drives 1.65 gears. Labbed by BBlades Bravo 1's 30's 5100 rpms 72mph (lots of slip)
Bravo-1 28's 5300 rpms 72-73mph

is there any gain to running 29P x 15.5" Hydromotive Q IV,s
I know nothing about these props?
help a brother out.

Well,

First of all 15.5% slip isn't (lot's of slip) especially with your hull. (previous identical set ups taken into consideration)
Second,
What is your ultimate desire? (Don't tell me everything) Speed at WOT or cruise speed and fuel economy?

Since you have talked about this before on this and other threads but didn't contact me,..... I believe we are dealing more with set up and your particular boat CG etc., other than just propeller issues.

28's are at 12.7% @ WOT. (what are the actual history of those props?)
What are the true speeds at for each at 4000 rpm?

29 Q4's will drop the R's in stock configuration and raise the stern. They may improve cruise speed as well.
We most likely have them for testing if you desire. We also have 5 blades that have worked on your hull.

Let me know if you wish to look at other options.

Brett

We have talked twice actually,, I'm not dissing BBlades infact you did balance my 30's out some so they ran more even but I did lose a little top end.. just a trade off.. My 30's you said are an older style Bravo-i.. I assume the slip numbers you are giving take into effect your backing the 30's to 29 and the 28's to 27 because knowing thats how the Bravo 1's run about a pitch under correct?.. Because on a pitch slip calculator its 14-15 on the 28s and about 18 on the 30's.. Hense my questions.
My goal is top end at wot thats why I asked the question aboutthe Hydros and the lift they tend togive in the stern.. I am a stepped V boat. But 312s are not light eiher.

29 pitch, 1.65g.r., 5100rpm, 72mph comes out to 15.17% slip. This really isn't too bad of a number. If the slip is reduced via propeller adjustments, the rpm may drop and the out come is the same speed. I'm suggesting there is most likely very little left on the table here.

My comment about set up is meant to cause you to think about prop shaft depth, prop rotation etc. I feel there may be more to be gained from this type of adjustment.

I fear going to a higher stern lifting propeller may cause even worse slip % issues. I do have some stock Q4 28's for testing if you like. These would allow us to see how the boat reacts to this style of geometry. The rpm will climb slightly but the added diameter may bring the slip down. It's just a question of wetted hull with the added stern lift.

Let me know if you would like to try them.

Brett