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  1. #1
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    2010 Mercury pro xs 225 fue pressure/ air pressure specifications

    Motor is a 2010 Mercury pro xs model #1225p73ed / serial # 1b802750 / 25 p tempest
    plan on doing a fuel and air pressure test, I have a fuel pressure gauge good for 100psi
    i believe air pressure is from port fuel rail and fuel pressure is from star boadd fuel rail?
    Also im going to check fuel pressure at the vst and also fuel pressure at the line before pulse pump.
    I believe specs were 90 psi for fuel pressure and 80 psi for air pressure?
    Whats the psi for fuel inline from primer ball to pulse pump? And how do you check low pressure fuel pump?
    Also do I check with the motor running or with the key on the start position?
    Been reading all the previous threads so just want to verify. Also does anyone know where I can get a repair Manual for this motor or know where I can buy one?
    I belive I’m having fuel pressure issues that’s why I want to test fuel pressures. Thanks in advance.


    running wide open throttle at 5600-5700 rpms after 1-2 minutes engine sputters, drops to 3800-4200 and feels sluggish. No beeps or anything. Beeps when first starting (check beep). When I shut if off after acting up I turn it back on imediarely and and full throttle and I have full power again but same issue occurs, loss of power after a minute or 45 secs. Smart craft gauge (digital) shows good voltage at wide open throttle, 14.0 v. Water pressure above 20 or around 20 psi. Motor has 167 hours , serviced motor at 165 hours new impeller, lower unit fluid, spark plugs, and fuel filter. Done by an experienced boat mechanic from my knowledge.
    Going to put a new primer ball and fuel line to pulse pump this weekend and check fuel pressures and air pressures. Any input would be nice.
    Last edited by KX1990; 02-24-2018 at 06:53 PM.

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    #2
    You must use DUAL (two) liquid filled gauges on the air and fuel rails, and read the pressures at the EXACT same time.

    There is no positive fuel pressure "for fuel inline from primer ball to pulse pump" the fuel is being sucked to the pulse pump.

    Get a Genuine Mercury Marine Service Manual, according to you motors serial number, from a Mercury Dealer.



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    #3
    Quote Originally Posted by Savage View Post
    You must use DUAL (two) liquid filled gauges on the air and fuel rails, and read the pressures at the EXACT same time.

    There is no positive fuel pressure "for fuel inline from primer ball to pulse pump" the fuel is being sucked to the pulse pump.

    Get a Genuine Mercury Marine Service Manual, according to you motors serial number, from a Mercury Dealer.
    why does the gauges need to be liquid filled? Also it has to be tested together as one gauge hooked up to the fuel and one gauge hooked up to the air pressure?

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    #4
    1. The needle will vibrate erratically and you won't get a 100% accurate reading.
    2. Yes.



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    #5
    Quote Originally Posted by Savage View Post
    1. The needle will vibrate erratically and you won't get a 100% accurate reading.
    2. Yes.
    I didn’t have 2 gauges so I went with 1 anyways the starboard fuel rail adapter was stripped so the gauge couldn’t go on anyways. So I tested pressures at the vst and I’m bouncing around 35psi. Checked the port fuel rail and I’m at 92 or so psi. Non fluid filled gauge. Anyways was running full throttle and I fell the motor sputter and drop rpms again. So I look and fuel pressure at port side is still at 92 psi with the engine sputtering. Unable to check starboard fuel rail the valve is damaged.
    So I disconnect he connector to the right of the vst and turn the key on engine off and no noise. Reconnect connector and fuel pump primes. However I disconnect left side connector that goes into vst and no changes. What’s the left connector for?
    Anyways I’m so tired of this issue I don’t have the time to keep going to the lake and test it. I set an appt for diag at c&c marine in Modesto. However it’s a 1 month wait. I have until March 23 to figure it out before I take it in.

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    #6
    I replaced the primer bulb with a new quicksilver brand primer bulb and replaced the line from bulb to motor about 3 feet (5/16 gray with blue writing) and I’m still getting same issue. Should I also do new lines from tanks to primer ball?
    i cut open my old fuel line and it seemed fine no delamination.

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    #7
    Yes, replace all lines at the same time.



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    #8

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    #9
    SO I paid $110 at a local boat shop, here’s what the repair order states
    ran diagnostic no fault codes found
    tested fuel pressure - good
    replaced check valve on lift pump/pulse pump test run good.
    cant see anything wrong.
    so I get the call to pick it up and I had about a 2 hours of daylight so I run to pine flat lake and run my boat.
    Sad to say that my issue is still present. Not only that it acts up even more now. Even feels like it’s misfiring.
    Could my coils or spark plug wires be bad but only act up after a load? Im pretty much lost in this situation.

    anyone know someone that would run the boat with me with the computer hooked up in the Central Valley area in CA?

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    #10
    fuel psi for pxs gray inj is 112 +- 2/air is 93 +- 2 ,correct plugs gapped correctly izfr6j ???? new fuel filter ??????/if you suspect its fuel psi you must monitor it when problem occurs,repair stb Schrader to monitor fuel psi,left connector is water sensor,remove red top filter [flash light] and look down in cavity for hose linning,coil could be bad, dout wires are, look in boot for rusty contact at coil or plug/ hope this helps ya JOE
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #11
    Quote Originally Posted by KX1990 View Post
    SO I paid $110 at a local boat shop, here’s what the repair order states
    ran diagnostic no fault codes found
    tested fuel pressure - good
    replaced check valve on lift pump/pulse pump test run good.
    cant see anything wrong.
    so I get the call to pick it up and I had about a 2 hours of daylight so I run to pine flat lake and run my boat.
    Sad to say that my issue is still present. Not only that it acts up even more now. Even feels like it’s misfiring.
    Could my coils or spark plug wires be bad but only act up after a load? Im pretty much lost in this situation.

    anyone know someone that would run the boat with me with the computer hooked up in the Central Valley area in CA?
    There's a diaphragm in the pulse pump that can crack cause intermittent problems, then tear and it's a no go, dead in the water. Just had mine replaced after three tech visits and two tows.

  12. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #12
    Sounds like attempts at diagnosing this are bouncing all over creation. Strongly suggest a Logical, Methodical approach.

    -Compression Test
    -Spark Test (and confirm proper plugs/gap/condition)
    -Fuel Quality, Delivery, and Air/Fuel Pressure Tests *

    * Need, as stated earlier a DUAL-PRESSURE, LIQUID OR GLYCERIN-FILLED GAUGE SET. You'll also need to obtain a new STB Rail fuel pressure fitting.

    Record pressures:

    -At idle
    -Under Acceleration
    -5/10/15 seconds after engine shutdown.

    Also note- it may be necessary to perform these tests immediately following the running problem/occurrence.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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    #13
    UPDATE
    so I took my boat to c&c marine in Modesto CA, they performed compression test, good. Checked spark plug gap, bad. Found spark plug gap at .032, he set them all to .042-.044. Further diagnosis he removed the fuel filter and found that there were small red chunks of the old fuel filter. the guy who did the previous work removed it damaged a few of the threads on the vst upper housing. He also found the red chunks inside the vst. He also noticed on the ear muffs temps didn’t reach 130 degrees so he swapped out both thermostats. Going to pick up the boat tomorrow so I’ll update tomorrow. seems like this is similar to what I’ve been seeing on the thread. So he said the red chunks from the old filter was clogging the float inside the vst causing fuel starvation.
    ran the boat at the ca delta and ran flawlessly. Happy that the issue is resolved. Back to fishing and enjoying the sunshine.
    Last edited by KX1990; 03-28-2018 at 09:44 PM.

  14. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #14


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

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    #15
    What was the outcome of you issue?

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    #16
    Its been 3 months, so my guess would be that he's happy.