what prop to try now??

formulaok · 11-18-2009, 08:48 PM

I have a formula 271 non step with a single bravo installation. Currently the boat runs 83 at 5600 with a 28 pitch non labbed bravo I. I am installing an imco 12 setback -3" raise extension box and wonder if the hering 5 blade bravo style would be the best place to start.

Before the extension box is installed, I currently have 5 1/4" from propshaft to keel. I am pretty sure the boat won't even come on plane after raising the x dim this much with a 4 blade.

anyone done something similar or have their .02?

Thanks in advance

jeffswav · 11-19-2009, 07:29 PM

I am not sure about your new setup. But I am getting ready to raise mine from a 8" depth to 5". I currently run a labbed 25 Mirage. Did your boat come with the drive set at 5.25"? Did you every try a Mirage on your boat? I will be interested to see what your outcome is. I think because of the angle it will be about 2 1/8" higher. I know some guys are running that high. Check out my thread on "What is your drive height?" under the "drives" section. There is a bunch of good info there.

BenPerfected · 11-19-2009, 10:34 PM

I think you can likely get on plane with your prop shaft about 2-2.5 below the keel. Use all your tabs and ease the throttle to as much as 3500-4000 RPM. If you don't like the answer, I would space down 1" and stay with the B1's. The spacer will be less cost than 5-blades and likely this set-up will give you better overall performance.

HTGMotorsports · 11-20-2009, 11:31 AM

Quote:

Originally Posted by formulaok

I have a formula 271 non step with a single bravo installation. Currently the boat runs 83 at 5600 with a 28 pitch non labbed bravo I. I am installing an imco 12 setback -3" raise extension box and wonder if the hering 5 blade bravo style would be the best place to start.

Before the extension box is installed, I currently have 5 1/4" from propshaft to keel. I am pretty sure the boat won't even come on plane after raising the x dim this much with a 4 blade.

anyone done something similar or have their .02?

Thanks in advance

From my experience you will have no problem getting on plane as the 12'' extension will put the prop deep in the water. You will probably like 5 blades and maybe need more pitch as the prop will be farther out of the water at running speed. I have a set of 31 5 blade Hering's for an XR shaft if you want to try. Rob www.htgracing.com

Philm · 11-20-2009, 02:36 PM

I have a different boat of course, but I get on plane with a 2.5" height and a labbed Bravo 1. It takes a long time, but it will get there. Just ease into it.

formulaok · 11-20-2009, 09:42 PM

thanks for the info. Rob, those Herings are probably going to be a good me, but I only have one screw and I doubt you'd want to separate the pair. How much do you want for them?

Griff · 11-21-2009, 03:21 AM

You need to run what you have after the box is added to get a baseline for what is needed.

formulaok · 11-22-2009, 10:07 PM

Griff you are right. I'll probably be able to coax it on plane with the 4 blade. No sense in buying props blindly.

AIR TIME · 11-29-2009, 12:23 PM

good luck there was a 25ol from germany that picked up a lot from the 3'' raised box went from 74 to 81 with a 525 merc, then he went up 2'' shortie but added a 1'' spacer for its final spot so I think he ended at 3 1/2. I have a konrad with box and am going from 7 5/8s to 3'', I think the boats with steps and notches can go higher under 3. I hope I WON'T NEED TO GO LOWER like 3 1/2''. hate spacers, I plan onstarting with a 30 px5 for base hoping to hit it just right haha. but have a 32b1 also and a 26 b1. if I TURN THE 30 at 6000 to 6400 its perfect. or the 32 at that rpm.