Go Back  Offshoreonly.com > Technical > Prop Talk
Is a prop slip of 7-8% realistic? >

Is a prop slip of 7-8% realistic?

Notices

Is a prop slip of 7-8% realistic?

Old 10-04-2017, 02:44 PM
  #1  
Registered
Thread Starter
 
Join Date: Sep 2014
Posts: 109
Likes: 0
Received 1 Like on 1 Post
Default Is a prop slip of 7-8% realistic?

Is a prop slip of 7-8% realistic?

We recently tried a new prop and got significantly better performance.
Our previous props were producing 16-19% slip (24 and 26 Bravo I props. 24, 26, and 27 Hydro props)

Then we tested a 21 Pitch Revolution 4 prop, 7% slip!
It is such a dramatic difference, I have to question the results.

Boat details:
1993 26' Velocity
Bravo XR 1.5:1
new 21 Pitch Revolution 4 (LH)
new tach 5700 rpm
2 independent gps showing 70 mph
Sonic24 is offline  
Old 10-04-2017, 03:57 PM
  #2  
Registered
iTrader: (2)
 
Join Date: Mar 2003
Location: Dallas
Posts: 3,064
Received 61 Likes on 22 Posts
Default

It is realistic but maybe rare. I am at 8% as well.

5400 RPM
1.5 Gear
28P
87 MPH
TxHawk is offline  
Old 10-05-2017, 05:32 AM
  #3  
Gold Member
Gold Member
 
Dave M's Avatar
 
Join Date: Oct 2000
Location: Hollywood, MD, USA
Posts: 5,652
Received 122 Likes on 77 Posts
Default

When I calculated the slip at WOT on the 24 Superboat I owned, I was getting 9-10%. That was under ideal circumstances.
Dave M is offline  
Old 10-05-2017, 06:42 AM
  #4  
21 and 42 footers
Platinum Member
 
t500hps's Avatar
 
Join Date: Sep 2004
Location: Richmond VA
Posts: 8,182
Received 119 Likes on 61 Posts
Default

After prop experiments I went from 18-19% to 10.5% in a 382 Formula......and 10 hours later trashed an outdrive. Slip isn't always a bad thing
t500hps is offline  
Old 10-05-2017, 07:04 AM
  #5  
Registered
 
Join Date: Oct 2016
Location: Buffalo, NY
Posts: 553
Received 1 Like on 1 Post
Default

Originally Posted by Sonic24
Is a prop slip of 7-8% realistic?

We recently tried a new prop and got significantly better performance.
Our previous props were producing 16-19% slip (24 and 26 Bravo I props. 24, 26, and 27 Hydro props)

Then we tested a 21 Pitch Revolution 4 prop, 7% slip!
It is such a dramatic difference, I have to question the results.

Boat details:
1993 26' Velocity
Bravo XR 1.5:1
new 21 Pitch Revolution 4 (LH)
new tach 5700 rpm
2 independent gps showing 70 mph
I had a 25 revolution on a Baja a few years back. It was like I put 27 pitch prop on. They definitely grab some water.
veloc410 is offline  
Old 10-05-2017, 07:09 AM
  #6  
Registered
 
Join Date: Oct 2016
Location: Buffalo, NY
Posts: 553
Received 1 Like on 1 Post
Default

Originally Posted by t500hps
After prop experiments I went from 18-19% to 10.5% in a 382 Formula......and 10 hours later trashed an outdrive. Slip isn't always a bad thing
Im getting quite a bit of slip on my props now and was worried about the same thing if I went to 5 blade. Twin 572's 30 pitch 4 blades sl4 and bravo one outdrives . After what you said I think I'll stick with the 4 blades .I get a lot of slip at cruise speed say 40 mph
veloc410 is offline  
Old 10-05-2017, 07:25 AM
  #7  
SB
Registered
iTrader: (1)
 
Join Date: Nov 2004
Location: On A Dirt Floor
Posts: 13,516
Received 3,088 Likes on 1,390 Posts
Default

Originally Posted by t500hps
After prop experiments I went from 18-19% to 10.5% in a 382 Formula......and 10 hours later trashed an outdrive. Slip isn't always a bad thing
I agree.
SB is offline  
Old 10-05-2017, 08:17 AM
  #8  
21 and 42 footers
Platinum Member
 
t500hps's Avatar
 
Join Date: Sep 2004
Location: Richmond VA
Posts: 8,182
Received 119 Likes on 61 Posts
Default

Originally Posted by veloc410
Im getting quite a bit of slip on my props now and was worried about the same thing if I went to 5 blade. Twin 572's 30 pitch 4 blades sl4 and bravo one outdrives . After what you said I think I'll stick with the 4 blades .I get a lot of slip at cruise speed say 40 mph
Yep, twin 540's/700 ft/lbs TQ. 32P bravos, 18-19%.........28P full size (15 5/8) maximus were 10.5%. Cruise speed increase was great (WOT speed dropped), but the drives didn't survive.
t500hps is offline  
Old 10-05-2017, 01:38 PM
  #9  
Registered
 
Join Date: Jun 2017
Posts: 76
Likes: 0
Received 1 Like on 1 Post
Default

Sometimes slip numbers are wrong.

example:
I switch from one 25 to another.
my slip numbers go down from say 13 percent to 9 percent.Looks good on paper but if my new prop actually has 26 instead of 25.Or my old one was actually 24 instead of the 25 it said then my slip numbers are almost identical to my old prop.
Warship2k15 is offline  
Old 10-05-2017, 05:23 PM
  #10  
Registered
 
Join Date: Oct 2016
Location: Buffalo, NY
Posts: 553
Received 1 Like on 1 Post
Default

T500 .Is that a fountain. I see step transom. How far below the deadrise are your propshafts??
veloc410 is offline  

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.