Like Tree0Likes

Trying to get rid of porpoising

Reply
Old 05-16-2011, 01:03 PM
  #1
Registered
Thread Starter
 
bigboat28's Avatar
 
Join Date: Dec 2004
Location: Ohio
My Boats: 2004 31 Formula PC and a 1988 28 Pantera for sale
Posts: 3,145
Default Trying to get rid of porpoising

I have a 28 Pantera with 425hp 454's and number III drives. Right now it has 4 blade 28 pitch props on it. It will only turn those to around 4200 rpm's and it porpoises bad. I was wondering if going to a set of 3 blade 27 pitch props would help it out? I have only used the boat for one weekend so far and the water was smooth so I don't know how bad the porpois is in rougher water.
bigboat28 is online now  
Reply With Quote
Old 05-16-2011, 01:06 PM
  #2
Registered
Thread Starter
 
bigboat28's Avatar
 
Join Date: Dec 2004
Location: Ohio
My Boats: 2004 31 Formula PC and a 1988 28 Pantera for sale
Posts: 3,145
Default

Sorry they are 26 pitch 4 blades right now.
bigboat28 is online now  
Reply With Quote
Old 05-16-2011, 01:57 PM
  #3
Registered
 
scarabman's Avatar
 
Join Date: Nov 2002
Location: TR, NJ
My Boats: 2000 33 Scarab AVS
Posts: 1,590
Default

You have too much prop for one. What shape are the ears on the current props? Does your boat have tabs? If so , at what deployment do they alleviate the porpoise?
scarabman is offline  
Reply With Quote
Old 05-16-2011, 02:20 PM
  #4
Platinum Member
Platinum Member
 
Join Date: Dec 2002
Location: Dallas, TX
My Boats: 1987 Scarab Panther
Posts: 2,117
Default

I think the 23-24 P will be close. If you can't find a set to test with, BBlades has a nice loan/swap program.

Last edited by BenPerfected; 05-16-2011 at 02:22 PM.
BenPerfected is offline  
Reply With Quote
Old 05-16-2011, 03:45 PM
  #5
Registered
Thread Starter
 
bigboat28's Avatar
 
Join Date: Dec 2004
Location: Ohio
My Boats: 2004 31 Formula PC and a 1988 28 Pantera for sale
Posts: 3,145
Default

K planes need to be about 3 to stop it and it does not run free at all, you can feel the bow being held down. Which props are better for porpoising 3 or 4 blade? The boat used to have 600 plus hp and ran in the 80's with these drives and props. The guy I bought it from put these 425 hp motors in it. Will weight in the bow help, you think?
bigboat28 is online now  
Reply With Quote
Old 05-16-2011, 03:58 PM
  #6
VIP Member
VIP Member
 
excalibur82's Avatar
 
Join Date: Mar 2007
Location: New Jersey
My Boats: 35 lightning
Posts: 910
Default

What diameter are your props now? If they are under 16 I would say try A larger diameter and down in Pitch.
excalibur82 is offline  
Reply With Quote
Old 05-16-2011, 04:07 PM
  #7
VIP Member
VIP Member
 
excalibur82's Avatar
 
Join Date: Mar 2007
Location: New Jersey
My Boats: 35 lightning
Posts: 910
Default

My 33 fountain had III's on it and I had the same problem. I went up in diameter and down in pitch. I had 26x16.5 and I picked up 8 mph. Felt like a different boat. I also tried some 29 x 17 three blades and they ran the same top end but lost some on the cruise.
excalibur82 is offline  
Reply With Quote
Old 05-16-2011, 04:54 PM
  #8
Registered
Thread Starter
 
bigboat28's Avatar
 
Join Date: Dec 2004
Location: Ohio
My Boats: 2004 31 Formula PC and a 1988 28 Pantera for sale
Posts: 3,145
Default

I think they are 15 3/8 x 26 now.
bigboat28 is online now  
Reply With Quote
Old 05-16-2011, 05:19 PM
  #9
Registered
Thread Starter
 
bigboat28's Avatar
 
Join Date: Dec 2004
Location: Ohio
My Boats: 2004 31 Formula PC and a 1988 28 Pantera for sale
Posts: 3,145
Default

So more diameter would increase transom lift, correct? Is that what I need to stop the porpoising, transom lift? Do I need to get 16 or bigger, or would a 15 3/4 3 blade be better than what I have?
bigboat28 is online now  
Reply With Quote
Old 05-16-2011, 05:21 PM
  #10
Registered
Thread Starter
 
bigboat28's Avatar
 
Join Date: Dec 2004
Location: Ohio
My Boats: 2004 31 Formula PC and a 1988 28 Pantera for sale
Posts: 3,145
Default

Excaliber, did you also have the same rpm problem or were you always able to turn around 5000? How many hp you have?
bigboat28 is online now  
Reply With Quote
Reply



Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 04:18 PM.


Copyright 2011 OffShoreOnly. All rights reserved.