throttleup

Chris288,

Keep in mind that when you run your slip numbers with a Bravo I propeller you need to reduce the pitch one inch from what is actually marked on the propeller. Bravo I propellers are not true to pitch so your 26P is really a 25P. Thsi gives you a slip of 13% not 17%. So it looks like your drive heigth is good and I would recommend a Hydro P5-X on your boat in a 25P. Hope this helps!

Julie

throttleup

Keep in mind that we have a Prop Fitting Program that is always availabe to you for testing!

Julie

Semper Fi

This stuff is really a science!!

Chris288

Thanks for the suggestion and info Julie,, if I run my #'s again using 25 and 27 I get a slip of 14 for the 26 and 15 for the 28... What are your feelings regarding giving a stock 27 p5x a shot and see what my numbers are and then have it labbed for extra rpm from there ??,, obviously if I'm looking into a 5 blade, holeshot, and midrange should be a given,, and at that point I'd be interested in top end only.. ?? Thanks Chris

throttleup

You could try the 27 but I think you will need something in the 25 pitch range with a 5 blade prop. The 27 would be a little low on rpm but you would get an idea how the boat handles with the prop. We are going to add a 25 to our test props. We should know by Monday.

The 25 should put you right at 5000 which is where we want the 496 HO to run for max speed. It's possible to pick up a little top end with the 5 blade prop for your application. I think it should do that right out of the box. After looking at your numbers we could look into lab finishing the prop, if necessary.

Matt

382 FASTECH

back to the original question here is my results,Formula 382 f2 race boat not as heavy in bow as yours. merc bravo 1 4 blade labbed 32", 26% slip.I could not get the boat to respond to trim at all.Then I put a pair of p5 hydro's 30"( non labbed) on and slip went down to 10% The boat responds unbelievable to trim I can lift the bow as high as I want even at lower speeds, and at wot it lifted the whole boat at higher speeds and never lost any top speed.I gained 7mph at 4000 rpm when cruising.Please remember my boat is set up different ,my x dimension is 2.5" higher than my buddies 382 formula and weighs 3000 lbs less.I would go with the maximus or p5x to help carry the bow.You will love how the hold the water, less slip.

Chris288

Thanks Matt,,,,,,, If a stock 25 would put me at 5,000, thats why I thought a 27 would be a better place to start,, I know it would be down on R's,, but then wouldn't the labbing bring it back into range ???? And then if I end up adding the Raylar heads to boost the H.O. from 425 to around 475-500 hp, I should still have enough prop ??.. Thanks again..

P.S. I would be interested in giving that 25 a shot if you end up adding it..

throttleup

Something important to keep in mind is if you put the Raylar heads on at what rpm does it produce the 475hp? If the heads move the hp up the powerband then you not need the taller pitch. The lower pitch may do it with an increase in rpm.

When we lab finish the P5X we don't see rpm increases like we do with Bravo 1's. The P5X will usually pick up about 150 rpm from a lab finish which is about 1 inch of pitch.

Matt

tomcat

Brett and Matt: Any comments about the use of Bravo, Maximus, P5 and P5X on cats running over 100 mph? I have been reading this and other threads about 4 vs 5 blades and my limited understanding would be that cats don't need any bow lift from the propeller.

bbladesprops

Troutly, yes I did and a response will be coming back asap.

tomcat, my responses were trying to explain the differences in multi bladed propellers versus propellers with less blades. Because certain propeller geometries induce stern lift, a boat not capable of carrying its bow may have issues running a 4,5, or 6 blade prop. It's like comparing a cleaver to a chopper. One carries the stern while the other carries the bow. As a propeller approaches the surface, it has less water to leverage itself against. The result is allowing the bow to drop. Some cat boats as well as vented v's don't need the bow lift because they pack air in the tunnel or ride on very aerated water.

This being said means in no way that a 5 or 6 blade won't work on your boat whatever it is. It just means the laws of physics show the more blades and or diameter will induce tail lift. If your rig can handle that, and the trim ability the specific multi bladed prop has built into it, you will most likely love the benefits they offer.

We know from testing and feedback, some of the boats that do and don't like them.

One cat known as a Hustler formally as a Talon, needs bow lift. It's one of those boats that just has its own personality. It is a awesome boat and in race configuration hauls a$$. But in a standard lay up and CG, it needs the correct propeller and rotation.

Multi bladed propellers came in to existence for certain applications, not all of them.

I hope this helps a little.