Go Back  Offshoreonly.com > Technical > General Q & A
22p to 24p swap and losing rpm??? >

22p to 24p swap and losing rpm???

Notices

22p to 24p swap and losing rpm???

Old 08-09-2010, 10:53 PM
  #1  
Registered
Thread Starter
 
Join Date: Apr 2010
Posts: 6
Likes: 0
Received 0 Likes on 0 Posts
Default 22p to 24p swap and losing rpm???

i have a 28ft commander deck boat and i bought it with a 22p on it and i was only pulling 57mph @ 4600rpm on a good day. Just put on a 24p this weekend and now im at 50mph @ 4100rpm. What could be the issue ?
freddyata is offline  
Old 08-09-2010, 10:58 PM
  #2  
Pirate of the Chesapeake
Gold Member
iTrader: (2)
 
Fenderjack's Avatar
 
Join Date: Aug 2006
Location: North Point Creek, Md.
Posts: 4,330
Likes: 0
Received 0 Likes on 0 Posts
Default

Ahhh when you go up in pitch you lose rpms

John jr
Fenderjack is offline  
Old 08-10-2010, 12:05 AM
  #3  
Registered
Thread Starter
 
Join Date: Apr 2010
Posts: 6
Likes: 0
Received 0 Likes on 0 Posts
Default

we talked to a few different people and they all said to run a 24 and we should do at least 60+...any ideas?
freddyata is offline  
Old 08-10-2010, 12:48 AM
  #4  
Registered
 
BY U BOY's Avatar
 
Join Date: Aug 2005
Location: HOUSTON ,TX
Posts: 8,779
Likes: 0
Received 1 Like on 1 Post
Default

What engine? how many hours?
BY U BOY is offline  
Old 08-10-2010, 01:10 AM
  #5  
Charter Member # 55
Charter Member
 
Griff's Avatar
 
Join Date: Oct 2000
Location: Omaha/LOTO
Posts: 19,518
Received 1,783 Likes on 884 Posts
Default

Originally Posted by freddyata
we talked to a few different people and they all said to run a 24 and we should do at least 60+...any ideas?
They were wrong. A 200rpm loss per inch of pitch increase is normal.

You were barely pulling enough rpms with the 22" prop.

What engine???
Griff is offline  
Old 08-10-2010, 08:54 AM
  #6  
Registered
 
PatriYacht's Avatar
 
Join Date: Jul 2002
Location: Waterford,MI
Posts: 2,867
Likes: 0
Received 1 Like on 1 Post
Default

It takes a lot of hp to turn a larger prop. It seems that you are propped pretty close.
PatriYacht is offline  
Old 08-10-2010, 09:27 AM
  #7  
Registered
 
Join Date: Sep 2007
Location: Bettendorf, Iowa
Posts: 1,053
Likes: 0
Received 0 Likes on 0 Posts
Default

you need to go down in pitch to increase rpm and put the prop at its most efficient rpm.... we need to know what engine you have to know what is its peak operating rpm range. the 22bravo1 is more like a 21. so a 21 3 blade would most likely act about the same. you may want to try a 19p mirage plus and mabye have it re-worked with a little more cup or pitch to about the 20 range to get you at that 48-5000 rpm range.
Fixxxer22 is offline  
Old 08-10-2010, 02:02 PM
  #8  
Registered
 
PatriYacht's Avatar
 
Join Date: Jul 2002
Location: Waterford,MI
Posts: 2,867
Likes: 0
Received 1 Like on 1 Post
Default

If it's a standard 454 not a Magnum, 4600rpm is the correct rpm.
PatriYacht is offline  
Old 08-10-2010, 05:57 PM
  #9  
Registered
 
Join Date: Sep 2007
Location: Bettendorf, Iowa
Posts: 1,053
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by PatriYacht
If it's a standard 454 not a Magnum, 4600rpm is the correct rpm.
4600 is a little shy. i thought mercruiser likes to run around 4800 for most of their applications.
Fixxxer22 is offline  
Old 08-10-2010, 06:19 PM
  #10  
Registered
iTrader: (1)
 
onesickpantera's Avatar
 
Join Date: Feb 2005
Location: Michigan
Posts: 4,388
Received 21 Likes on 10 Posts
Default

PatriYacht is correct. Standard 454 with cast internals has an operating range of 4200-4600 and the 454 Mag is 4600-5000. So if he has the non-mag engine he is on the money with 4600 rpm.
onesickpantera 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.