Rage Prop Question
05-07-2012, 03:28 PM
#1
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Rage Prop Question
running a 30p labbed at 5500 rpm and only seeing low 80s gps
675hp 690 TQ Is prop slip a problem here? I figured I would get more top speed out of her. 01' stepped hull. Also have a 32p stock that spins at 5100 around the same speed.
I am running a bravo one now but have a xr with sportmaster lower sitting in the garage.
675hp 690 TQ Is prop slip a problem here? I figured I would get more top speed out of her. 01' stepped hull. Also have a 32p stock that spins at 5100 around the same speed.
I am running a bravo one now but have a xr with sportmaster lower sitting in the garage.
05-07-2012, 04:34 PM
#2
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Hi Andy,
I just ran your numbers through one of the better calculators and showed this:
running standard 1.5 gear ratio
I am using 29" actual pitch for the B1
82mph since you didn't say exactly what mph
a theoretical speed of 101
slip % of 19
using 30"s of pitch
104 theoretical speed
21% slippage
I would say your propellers will need some cup added to bring the slip #s down. You have a fast hull and plenty of power. You just need to lock up your props more efficiently.
I doubt if your boat has any hook in the bottom, but it's not impossible. You may want to get a 4' level and check your pad a strakes. It should fit nearly flush from the transom forward.
Also, carrying weight in front of the CG/step on our boats does slow them down.
Regards,
Steve
I just ran your numbers through one of the better calculators and showed this:
running standard 1.5 gear ratio
I am using 29" actual pitch for the B1
82mph since you didn't say exactly what mph
a theoretical speed of 101
slip % of 19
using 30"s of pitch
104 theoretical speed
21% slippage
I would say your propellers will need some cup added to bring the slip #s down. You have a fast hull and plenty of power. You just need to lock up your props more efficiently.
I doubt if your boat has any hook in the bottom, but it's not impossible. You may want to get a 4' level and check your pad a strakes. It should fit nearly flush from the transom forward.
Also, carrying weight in front of the CG/step on our boats does slow them down.
Regards,
Steve
Last edited by Steve Zuckerman; 05-07-2012 at 04:37 PM.
05-16-2012, 09:18 PM
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Send your B1 to Merc for labbing. I had nearly same setup, ~750hp w/ labbed 32 (from merc, they know their stuff). Got me high 80s all day, low 90s in perfect conditions.
Another local guy tried my prop w/ ~650hp at Mead with similar results, adding 7-8mph to his so called "labbed" 28 that wouldn't turn as many revs as my Merc labbed 32. Get some gps #'s, revs & call them. They are a little more expensive, but it's right on what they say. In the end I think I was 17-18% slip.
Another local guy tried my prop w/ ~650hp at Mead with similar results, adding 7-8mph to his so called "labbed" 28 that wouldn't turn as many revs as my Merc labbed 32. Get some gps #'s, revs & call them. They are a little more expensive, but it's right on what they say. In the end I think I was 17-18% slip.
