Like Tree0Likes

fuel pump pressure

Reply
Old 07-04-2011, 06:17 PM
  #1
Ginger or Mary Ann?
Charter Member
Thread Starter
Trade Score: (1)
 
US1 Fountain's Avatar
 
Join Date: Oct 2000
Location: Lafayette. IN
Posts: 10,843
Default fuel pump pressure

Do the mechanical stock pumps always pump same pressure, or does it increase with rpm?

How much pressure can a Q-jet take before it unseats?

Thanks


added:

Is it possible for a stock Merc high volume pump to put out 20psi at 2000rpm? Curious if a buddy was sold the wrong pump.
__________________
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.

Last edited by US1 Fountain; 07-04-2011 at 06:40 PM.
US1 Fountain is offline  
Reply With Quote
Old 07-04-2011, 07:03 PM
  #2
Registered
 
Join Date: Jun 2011
Posts: 197
Pump Pressure

Stock pump about 5 to 6.5 lbs depending on the RPM . Anything over that your asking for problems. Damaged needle and seat bent float arms from fuel comming past the seat. If your going to run a high volume pump put in a fuel regulator and set it about 5 to 6 lbs.
BAD ASS SCARAB is offline  
Reply With Quote
Old 07-04-2011, 07:13 PM
  #3
Registered
 
Join Date: Feb 2009
Posts: 319
Default

The pump volume increases with rpm but the presure should not exceed 7 psi on a stock mechanical fuel pump. Sounds like the pump is wrong or defective.
Boat1 is offline  
Reply With Quote
Old 07-04-2011, 07:35 PM
  #4
Ginger or Mary Ann?
Charter Member
Thread Starter
Trade Score: (1)
 
US1 Fountain's Avatar
 
Join Date: Oct 2000
Location: Lafayette. IN
Posts: 10,843
Default

Ok, thanks guys.

This is a buddies boat been working on last couple weekends. stock '88 454. Dumps fuel past N/S. tried new kit, float and carb body, no change, thus eliminated carb as the culprit. He just put a press gauge on it today.
__________________
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
US1 Fountain is offline  
Reply With Quote
Old 07-04-2011, 09:58 PM
  #5
Platinum Member
Platinum Member
Trade Score: (3)
 
MILD THUNDER's Avatar
 
Join Date: Jul 2004
Location: chicago
My Boats: 38 Fountain
Posts: 10,797
Default

Quote:
Originally Posted by US1 Fountain View Post
Ok, thanks guys.

This is a buddies boat been working on last couple weekends. stock '88 454. Dumps fuel past N/S. tried new kit, float and carb body, no change, thus eliminated carb as the culprit. He just put a press gauge on it today.
I get 8psi at idle. 1050 Dominator, holley 120GPH six valve marine pump. High flow needle and seats, no problems.

However, you are working with a different animal. Sounds like he may be needing a pump.
MILD THUNDER is offline  
Reply With Quote
Old 07-05-2011, 11:00 AM
  #6
Ginger or Mary Ann?
Charter Member
Thread Starter
Trade Score: (1)
 
US1 Fountain's Avatar
 
Join Date: Oct 2000
Location: Lafayette. IN
Posts: 10,843
Default

Quote:
Originally Posted by MILD THUNDER View Post
I get 8psi at idle. 1050 Dominator, holley 120GPH six valve marine pump. High flow needle and seats, no problems.

However, you are working with a different animal. Sounds like he may be needing a pump.
I agree now that we know what the pressure actually is. I didn't think the mechanical pump was capable of that high of a pressure, so it never entered my mind as the problem.
A new pump is on it's way now.
__________________
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
US1 Fountain is offline  
Reply With Quote
Old 07-06-2011, 10:25 AM
  #7
Registered
 
Join Date: Jun 2011
Posts: 197
Default

US1 The slinkie joke is some Funny s##t thanks!
BAD ASS SCARAB is offline  
Reply With Quote
Old 07-06-2011, 10:44 AM
  #8
Ginger or Mary Ann?
Charter Member
Thread Starter
Trade Score: (1)
 
US1 Fountain's Avatar
 
Join Date: Oct 2000
Location: Lafayette. IN
Posts: 10,843
Default

...
__________________
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
US1 Fountain is offline  
Reply With Quote
Old 07-06-2011, 11:49 AM
  #9
Registered
 
Join Date: Feb 2011
Location: Seattle, WA
My Boats: 1995 mirage intruder 217
Posts: 101
Default

what kind of volume and or pressure will a factory mechanical pump from a 502mag off the water pump give???

will it support a 502 carb motor with a 800cfm holley without the electric pump that is high pressure for the efi
morrowcarl72 is offline  
Reply With Quote
Old 07-06-2011, 05:33 PM
  #10
Offshoreonly Advertiser
Offshoreonly Advertiser
 
Mbam's Avatar
 
Join Date: Mar 2001
Location: Pompano Beach FL, USA
My Boats: 1972 Cigarette 36 race
Posts: 2,034
Default

Some of the OEM Merc pumps are doing just that - too much pressure. We have warrantied a bunch.
__________________
Marc

www.mercruiserparts.com
www.go-fast.com
www.bammarine.com
www.cyborgtransmissions.com
It's alive -www.BoatStuffExpress.com - additional 10% discount for OSO members
Mbam is offline  
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 03:09 AM.


Copyright 2011 OffShoreOnly. All rights reserved.