Thanks! Trying to get this right, but props are ore art than science it seems.
What is your RPM range, and what is your drive ratio? I was thinking that a 24-26 pitch would be my starting point. I have the 1.5 ratio drives.

jeff

You are going to be closer to Sonic30ss's props. I ran a 27x20x18rake 6 blade with 1100hp /1200ftlbs trq(1.56 ratio)

Thanks!

runs well, only thing left is prop tuning to get slip numbers down.
Hauling boat for the season tomorrow, having props done over the winter.

peak Tq @3900
peak hp @ 5200
1.5:1 drives
Jim Hering spec’d the props, he’s pretty good at props 😉

Perfect, thanks.

And apologies if I keep asking the same questions, Im just trying to get it right this time!

-j

What speeds have you seen? I really interested in the cruising speeds/RPM, but top Speed is of course a big question too! thanks!

speeds are not where they should be yet, need to add some cup due to too much slip.

42mph @ 4000
50+ @ 5500
where it was before cupping props and destroying B3 drives

expecting
50ish at 3700ish
62+@5200

Yes, I was expecting to see better numbers too. When I used the Go-fast BAM speed calculator for the B3s, it comes up real close to actual speeds.
https://www.go-fast.com/Knowledge-ba...eed-calculator
Which is The Square Root of (Total Shaft Horsepower / Weight ) plus the crouch hull type factor. I used 250 crouch as that was what worked out using the stock config.I used this calculator to get the estimated speed based on HP only. Crouch constant is a common factor used to estimate hull speed based on hull type, length etc.

Then I use this calculator to get the mathematical speed based on prop/ratio/rpm:
https://goodcalculators.com/boat-prop-calculator/

b3 2.0/24p 4800rpm Hull constant of 250
Bam predicts 48mph
Actually attained 45mph
Works out to about 16% slip.

Same math should apply to the Surface drives:
Arnesons, 1.56/24p 4800rpm est 16% slip
BAM predicts 58mph @3600 41mph

Sounds like I may be optimistic with the 24pitch. But could it be that you may have under propped? I dont wish to run above 4800 rpm. A 21p puts my est speed at a less than desirable 51mph per the math. I had planned to use a 24p......

For me with B3 2.0 28 pitch with cup added. (before Bblades worked the props I was having cavitation burns so bad I was loosing chunks of prop)
3900rpm 45-47 mph
5200rpm 55 mph




As far as the current set up, the props were chosen based on experience from Rik and Jim Hering trying to make Excal’burs and 400SS run with the Arneson. I’ve used the same formulas you’ve used on this boat and others and they are pretty close when equipped with alphas and bravos.
I’m going to reserve judgment until I have current props scanned and reworked.
Ive seen amazing results from proper prop tuning, amazing as in “this is like a different boat” results