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fuel pressure from fuel pump?

  Discussion Boards > Boating Angler
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Joined: 10/18/2004
Posts: 368
Location: sayville
 posted 07/27/2005 11:14 PM  


Anyone know what the pressure should read on the line coming out of the fuel pump. 5 lbs? I am troubleshooting a fuel related problem and want to see if i'm getting the right pressure supply.

I plan on rigging a "T" in the line and put on a small guage to read the fuel pressure.

If this isn't the problem then im afraid I might have one of those "fuel problems" that everyone is facing.

Joined: 08/04/2003
Posts: 199
 posted 07/28/2005 07:41 AM  

I have a 15 hp merc 4 stroke kicker, carb, 3 - 6 psi. The 6.2 mpi is fuel injected and the pressure is 45 psi.
I believe that some of the new OB's, Optimax and Yamaha HPDI are in the 400 - 800 psi range.

Joined: 10/18/2004
Posts: 368
Location: sayville
 posted 07/28/2005 01:20 PM  

I have a 150HP Merc OB, carb. I've heard it should be around 5 -7.

Joined: 03/03/2002
Posts: 30
 posted 07/29/2005 06:54 AM  

I am not an expert, but I had the same problem and watched the mechanic test mine in the same manner you describe. He said it is not just the pressure but how long it takes to generate it, the gauge should come right up. If it takes a while it may indicate a problem.

Mine came up slow, I changed out the three fuel pumps and it made a huge difference in performance.

Joined: 10/18/2004
Posts: 368
Location: sayville
 posted 07/31/2005 08:57 PM  

alright fellas, tested it out with a guage. The guage read 12lbs when the line was primed with the bulb. When I started the engine, i watched the pressure drop, 10,8,4,0 and thats where it stayed. To make a long story short, turns out when I rebuilt the fuel pump I put the gaskets where the diaphram should be and the diaphram where the gaskets should be. Stupid @$$.

I guess I shouldn't have rushed this job.....

Joined: 08/23/2002
Posts: 4205
Location: Newton, NH
 posted 08/02/2005 01:38 AM  


Sounds like you found it, but it's only a few lbs of pressure on a carb engine.

The way to test it is to disconnect the line that feeds the carbs, pull the MOB kill switch to prevent sparks/fires/destruction and crank the engine while observing a steady pulse of fuel exiting the pump.


"Kids, don't try this at home."
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