OK I'm spinning a 27 hdromotive QIV 5200rpm with a 1.5 bravo1 at 70 mph GPS and my slip #'s are way high....like 21. At 1st I thaught my rpms were 2 low but now im getting 5200 out of it when running light, but not much faster. Runs very consistant 70 even runnin heavy with lower rpms like 5000, just wondering if labbing would give me more speed. If I calculate for like 12% slip it wold run 78. Ive seen 72 in light chop but thats it. Anyone have similar #'s? Juie?? Bblades??thanks guys?

I wold try to figure out why the slip is so high. That boat shouldn't run with so much slip. The prop you have is a good prop for the boat but something isn't quite right.

I would work on the boat before putting money in the prop. Lab finishing is not what you need right now. Prop work should be one of the last things you do.

Have you tried other props?
Has the prop you have now been worked in the past?
What motor or modifications do you have?

29 fountain fever 502 mag mpi with lightning headers, ported edelbrock heads, roller rockers, reprogrammed pcm. runs like 69 and some change all day at 5000 then 70 at 5200. either way slip #s are high. Im guessing my motor is similar to an HP500 or 525. motor runs great prop does blow out on hard acceleration or hard turns if it helps.

lilredboat,
I have a boat named just red boat.

I have similar problems. with 33' Avanti my RPMS are 5000 with the Bravo 24".s. (Twin 496 HO) Tried the Hydros 25". No good. same RPM slower speed, but I don't know the slippage. How do I calculate it anyways?
WHat boils down to is the Bravos actually have more surface area, but in reality only 23" pitch +-, I have researched the labbing issue, but prop. type and size is more important at this time. I been very lucky on other boats running cleavers, even on standard drives. What do you think Jullie?? IT seems that my boat needs more bites from the props and may be same with lilred....

Mark

I'm try to run and work with what ever you sent down for me at Ramada.
WE might need to try the 26' B's

so anyone ever have 21% slip?? If so did labbing help?

Try a Merc Bravo 1 prop.
If your slip is still real high then maybe a 5 blade.
Your drive may be set real high too and lowering the prop shaft with a drive spacer should lower slip.

Labbing the Hydros right now would require major mods. and isn't the right thing to do. I still wonder if the Hydro's haven't been reworked or repaired at one time.

Try some Bravo 1 props too. If the slip is still high, we may have a bottom issue or a CG and or X dimention issue.

yeah my x dim is real high, would a spacer slow me down by being deeper in the water?? Or will the better bite make up for it?