I am concerned that the diameter of the bravo one is too big- like I said my old MACH stern drive 28P prop, im certain had more slip- pitch seems correct and calculating from 1.3 - 1.5 though, Im correct there, no??!!

I most certainly would agree- however, the XZ drive is a 1.25" shaft, so the Mach prop was fixed at 1' shaft- no hub, besides going from 1.3 to 1.5 calculations say a 32P
prop would be very close-( i was able to get 32P AND 30P Bravo one props at the the same time and tested both, i went all the way down to 28P and got 6,000 rpms,
but barely hit 85mph

probably mid 90's era Bravo one- plus of course, it was converted to Bob's Nose cone. I worked quite well with old set up- that's why im puzzled- like i said- im still feeling like if I made the Bravo One into a 14 1/2 diameter- then slippage would be much closer to the old setup. imho. ( just don want to start chopping up a prop before I'm certain. I have looked everywhere for a smaller diameter prop, with 1.25" capability at 32P something in the gut is listing that way?

I was hoping that might be true, the XZ's dual pickup- does that change anything??

sounds like its narrowing down to a smaller circumference prop, 32P being correct prop- just need more slippage for lighter boat- with the same gearing of sorts- wish it could be that simple. The only other factor- i'm wondering if slightly stepping up REVS on the bm250 is possibly causing to much drag on engine- maybe overthinking that, lol. AND I KNOW at least, I should have an 8-71 ideally- just wanted to get through this summer- and was thinking it would be acceptable- since I was content with the old setup hitting 95ish. when I get the 8-71 than I feel ill be at 100+ and then I'm done/happy. maybe HaHa.
of course providing i can get past this,
I just want to say thanks to everyone pitching in to offer feedback, maybe this one's more fun figuring out than others. wishful thinking- lol.

originally my boat tech/shop calculated i was at 10-11% slippage- with old setup- i believe we were using 5600 @ 95ish MPH

btw, like i said before- im not cavitating at all- out of hole with new setup- however, I did with old setup- manageable - since I was hitting a decent speed.

For some reason I was thinking it was only a 5mph diff. 10 is quite a bit more.

I suspect it's a few compounding issues robning you of your 10mph.

The BM250 at 2.22over is really heating up the charge compared to your slower pulley.
You're not in your max power rpm range.
Using a larger diameter prop at those speeds.

It's always nice to have a air temp sensor in the intake manifold even just for testing etc.

I have a B&M INFO magazine from 1990. I'll dig it up and see if it has info on BM250 speeds. Unfortunately, getting blower efficiency charts is hard to find compared to turbos.

STOP…..go back to what SB said.

you changed way too many variables AND went Up in pitch by 4 in and nearly an inch in diameter.

the calculations called for a 32 pitch, after switching from 1.3 to 1.5, that would not seem to differ much, I tried a 30p and I got my rpms back up- yet still 85mph-

Im beginning to suspect the diameter is too big or too heavy and dragging- not sure- I get you though, hence why I'm here, however, correecting if Im wrong, i would not thinnk the twin carbs would matter much, Im temped to go back to the 1.3 drive and mach stern prop (14 1/2 X 29P) easy enough to do- would confirm engine running
optimum still- just spit balling - your thought's ?