Prop help
 

I started a thread a while back regarding prop help with not much or any response. What would put me in the neighborhood of 6,200-6,300 trimmed at WOT?

I’m re powering a 12m ftn. Engines are NA 565’s. Should be close to 740/750 hp at 6,300 + or -. SM3 drives I believe to be 1.5 ratio and Bam cyborg 1350’s which I need to confirm also however pretty certain 1:1.

Props that came with boat are clever 15 3/4x27. Previous owner claimed to only run 4,500 with SC 468’s with BM 250’s. I would have guessed to be around 625 however have no way of knowing for certain.

Any help would be great. I would like to start somewhere at least somewhat close. Tks

John

Current props I would have thought should be close however the previous builds/power tell me different.

17" pitch??? with 625hp and only 4500rpms??? Something is off.

Or 17* rake?? and ?? pitch??

thats what I thought Griff but all being new to me with boat and estimating previous owners platform. I estimated power on low side if anything I would think although I do recall being told the boost gauges weren’t working. During the few trips out with those builds. I’m kinda in the dark here.

https://cimg8.ibsrv.net/gimg/www.off...b1194223f.jpeg
https://cimg6.ibsrv.net/gimg/www.off...60d0ab8c1.jpeg
https://cimg2.ibsrv.net/gimg/www.off...d673b0fab.jpeg

Typo on original post. Meant 27 not 17. My mistake. Going to edit OP.

Why wouldn't you try what you have and then make the change if necessary,

I would and probably will if I don’t get any advice. I just assumed I’d be way off on rpm’s (low). Hate to launch it in spring and only turn 5,200 or something way off. If I was off 300 to 400 etc would be fine and adjust from there. I think at one time this same boat had 850 super cat engines and used same props. Once again 2nd hand info though.

It just seems like there are to many variables at this point. It would be nice if someone like Blades would let you try a few.

That makes more sense for sure.
BBlades only check the prop talk section so maybe post there.

I was originally going to however it doesn’t get frequented as much. Think the last post was in October however I’ll try.