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Decreasing prop slip on 31/32

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Decreasing prop slip on 31/32

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Old 09-18-2016 | 09:09 PM
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Default Decreasing prop slip on 31/32

I have a 93' 31 thunder
5400 rpm
1.5 gear
24 pitch Bravo's
67.5 GPS
@17% slip.

Tried multiple trim positions kinda found the sweet spot I think. To reduce slip are my only options to step up to 5 blades?.

Any advice is appreciated
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Old 09-19-2016 | 03:41 PM
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How much HP?
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Old 09-19-2016 | 03:51 PM
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@400 each
454 mags 365 hp w/ 420 cams, 9.3:1 lil more goodies ect.
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Old 09-19-2016 | 04:09 PM
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17% slip is good! less slip = more speed but harder on the drives,, 5 blades will slow you down you could try a 26 labed 4 blade
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Old 09-19-2016 | 04:54 PM
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I thought 17% was hideous. I just assumed @ 12% would be more like it. I am not to concerned about top speed, would like to get slip down and if I were to use 5 blades I would think my cruise mph would go up some what, most of the time the boat is ran 3000-4000 rpm. But I am up for any thoughts from fellow members
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Old 09-20-2016 | 01:47 AM
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Actually you are closer 15% slip. Bravo props are stamped heavy on pitch and are really .5-1" less than stamped. Use 23.2 for your pitch.
15% slip is pretty decent and about average for most 32's I've read about.

I'm at about 12-13% from cruise through WOT. I would attribute my lower slip numbers to having extension boxes and my props being BBlades labbed for the boat.

Last edited by Griff; 09-20-2016 at 01:51 AM.
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Old 09-20-2016 | 06:31 AM
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Are the drives in the original positions or did you move them up? In other words is it the original X-dimension?

Originally Posted by mountainmadness
@400 each
454 mags 365 hp w/ 420 cams, 9.3:1 lil more goodies ect.
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Old 09-20-2016 | 08:11 AM
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This was the boat designed for outboards. I think the first owner changed his mind and went bravo/big blocks. I beleive he rigged it so I don't know if it is setup like factory. Tonight I will see my propshaft to bottom relationship so we have a idea.
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Old 09-20-2016 | 08:15 AM
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Originally Posted by Griff
Actually you are closer 15% slip. Bravo props are stamped heavy on pitch and are really .5-1" less than stamped. Use 23.2 for your pitch.
15% slip is pretty decent and about average for most 32's I've read about.

I'm at about 12-13% from cruise through WOT. I would attribute my lower slip numbers to having extension boxes and my props being BBlades labbed for the boat.
Maybe I am not to far off then. I need a set of props to bring my rpms down to 5200 anyways and would love to pick up midrange 3-4 k cruise mph. First big twin boat so this is my first rodeo. Came from a @90 mph 18' sbc alpha boat lol
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Old 09-20-2016 | 05:01 PM
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If your after mid range speed not top end and want the rpms down then try a 26 bravo 1 and you should get what you want maybe a bit more rpm drop but faster mid range
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