Go Back  Offshoreonly.com > Owners Forum > Baja
More power from My 7.4MPI´s >

More power from My 7.4MPI?s

Notices

More power from My 7.4MPI´s

Thread Tools
 
Old 05-22-2011 | 04:51 PM
  #1  
Teo
Thread Starter
Registered
 
Joined: Aug 2009
Posts: 166
Likes: 0
Default More power from My 7.4MPI´s

Hi. I just went from Mirage Plus 23´s to Bravo 24´s on my 29 OL. The top speed is exactly the same, 61 miles because it wont reach 4.600 rpm with the bravos.
I did gain around 5 miles at 3.500 rpm wich is great but it would be nice to get just a little more power out of them so they reach 4.600 rpm with the bravos in an easy and sheap way.

Is that possible somehow with other exhaust or something or should I just forget it?


Sorry about my english, I´m from Sweden.
/Teo
Teo is offline  
Reply
Old 05-22-2011 | 05:24 PM
  #2  
JasonSmith's Avatar
Registered
20 Year Member
 
Joined: Feb 2005
Posts: 4,333
Likes: 5
From: USA
Default

Those motors are RPM limited to 4850 I think. I would expect the same speed out of the two propellers as they are both very close in pitch.
The gain you saw at 3500 RPM is typical of a 4 blade propeller. They tend to increase cruise speed more than top end.
I think that the 24p Bravo 1 would get you a few more MPH by having it lab finished, but for the HP you are running I wouldn't expect much more than 62-64 mph out of that boat with that power.
JasonSmith is offline  
Reply
Old 05-22-2011 | 05:29 PM
  #3  
Teo
Thread Starter
Registered
 
Joined: Aug 2009
Posts: 166
Likes: 0
Default

Originally Posted by JasonSmith
Those motors are RPM limited to 4850 I think. I would expect the same speed out of the two propellers as they are both very close in pitch.
The gain you saw at 3500 RPM is typical of a 4 blade propeller. They tend to increase cruise speed more than top end.
I think that the 24p Bravo 1 would get you a few more MPH by having it lab finished, but for the HP you are running I wouldn't expect much more than 62-64 mph out of that boat with that power.
Ok. I think mine are limited to 4.650 and with the bravo´s they only reach 4.300.

Do you think it will drink much more gas with the bravos?

Last edited by Teo; 05-22-2011 at 05:41 PM.
Teo is offline  
Reply
Old 05-22-2011 | 09:36 PM
  #4  
JasonSmith's Avatar
Registered
20 Year Member
 
Joined: Feb 2005
Posts: 4,333
Likes: 5
From: USA
Default

Originally Posted by Teo
Ok. I think mine are limited to 4.650 and with the bravo´s they only reach 4.300.

Do you think it will drink much more gas with the bravos?
The RPM range will be on the valve cover with all the other information on the engine.
It sounds like you're over propped.
JasonSmith is offline  
Reply
Old 05-23-2011 | 12:15 AM
  #5  
Registered
 
Joined: Apr 2005
Posts: 2,957
Likes: 1
From: www.bajaboatowners.com
Default

Originally Posted by Teo
Hi. I just went from Mirage Plus 23´s to Bravo 24´s on my 29 OL. The top speed is exactly the same, 61 miles because it wont reach 4.600 rpm with the bravos.
I did gain around 5 miles at 3.500 rpm wich is great but it would be nice to get just a little more power out of them so they reach 4.600 rpm with the bravos in an easy and sheap way.

Is that possible somehow with other exhaust or something or should I just forget it?


Sorry about my english, I´m from Sweden.
/Teo
Have the Bravo's labbed by Bblades or a propeller shop near you. This will gain you around 200-250 rpm's as well as possibly increase your current speed.

It's also possible altitude or elevation is effecting it. You should be able to spin 24's with 7.4L MPI's
Irishtornado is offline  
Reply
Old 05-23-2011 | 07:53 AM
  #6  
Teo
Thread Starter
Registered
 
Joined: Aug 2009
Posts: 166
Likes: 0
Default

Originally Posted by Irishtornado
Have the Bravo's labbed by Bblades or a propeller shop near you. This will gain you around 200-250 rpm's as well as possibly increase your current speed.

It's also possible altitude or elevation is effecting it. You should be able to spin 24's with 7.4L MPI's
I will do that. We have a propp-guru here i Sweden called "Propeller Björn". I will call hin right away.

Thanks.
Teo is offline  
Reply
Old 05-23-2011 | 08:58 AM
  #7  
Registered
15 Year Member
 
Joined: Apr 2007
Posts: 1,130
Likes: 2
From: Northern, KY (Cincinnati) Lake St Clair, MI Norris Lake, TN
Default

I ran 62 MPH with 23" mirage on my old 29OL with 7.4s. It would flirt with 63 every once in a while. I also had 22" 4 blades and it was quicker, but would bump the rev limiters from time to time with a light load. I think labbed 24"s would be perfect on that setup. You only need to pick up about 200 RPM.
Baja_342 is offline  
Reply
Old 05-23-2011 | 09:24 AM
  #8  
Custom Interiors & More
 
Joined: Jun 2008
Posts: 1,742
Likes: 2
From: Bucyrus, OH.
Default

Originally Posted by Baja_302
I ran 62 MPH with 23" mirage on my old 29OL with 7.4s. It would flirt with 63 every once in a while. I also had 22" 4 blades and it was quicker, but would bump the rev limiters from time to time with a light load. I think labbed 24"s would be perfect on that setup. You only need to pick up about 200 RPM.
I think I tried every prop make on my 29ol with 7.4 MPI's including 22, & 24 Hydro 4 blades. The 25 Mirage Plus labbed is very fast if the engines are still strong, but my overall favorite is the labbed 24 Bravos.
XT-Innovator is offline  
Reply
Old 05-23-2011 | 09:36 AM
  #9  
Teo
Thread Starter
Registered
 
Joined: Aug 2009
Posts: 166
Likes: 0
Default

Then it seems that I´m on the right track. How about the fuel consumption on Mirage 23P vs Bravo 24?
Teo is offline  
Reply
Old 05-23-2011 | 09:39 AM
  #10  
Registered
 
Joined: Apr 2005
Posts: 2,957
Likes: 1
From: www.bajaboatowners.com
Default

Originally Posted by Teo
Then it seems that I´m on the right track. How about the fuel consumption on Mirage 23P vs Bravo 24?
If your concerned about fuel keep it under 3500 rpm's any Big Block is going to burn fuel over that.
Irishtornado is offline  
Reply


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

Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.