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  1. #1
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    1997 225 Mercury Pro Max

    Asking for my brother so I don't have a serial #...

    Totally rebuilt over the winter. All new fuel lines and 360* hose clamps from Mercury. Has had it out a few times and he cannot get the primer bulb hard. Engine starts and runs great. He tries to pump the bulb throughout the day but with no success. Now the kicker, after he puts the boat in the garage he'll pump the bulb and it will get hard... He's replaced the new bulb with a newer bulb but still gets the same results... Any ideas???... Dan

  2. Member
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    #2
    Some bulbs are shy and don’t get hard in public
    Mercury 2002 200hp Carbed Saltwater
    OT566776
    2002 Cape Horn 22' Bay

  3. Banned
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    #3
    I thought that was bladders... Dan

  4. Member
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    #4
    Sounds like it has something to do with the angle of the boat, which is usually different when in the water as compared to on the trailer. Could be anything from floats (if the motor is carved) to fuel pickup in the tank having a split in the hose. Certainly needs to be resolved as running one of those lean will get real expensive real quick at that RPM. From experience.
    2008 Bass Cat Pantera Classic
    2014 Mercury Pro XS 200

  5. Member lpugh's Avatar
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    #5
    Wont get hard if the motor is running, did not see anything about engine off when pumping bulb, If motor is off keep pumping and check the vst vent for fuel coming out of it. If not disconnect the fuel line from the pulse pump and plug it, will it get hard now. If not you have a bad bulb or a leak between the bulb and the tank. Vacuum test as required
    Last edited by lpugh; 07-18-2019 at 08:18 PM.
    Thank You Leon Pugh

  6. Banned
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    #6
    This is how he explained it to me the other night... After removing transom tie-downs at the ramp, before launching he'll try to prime the bulb but it won't get firm. He'll idle out and try again with the engine running in neutral, still on luck, he's tried it after idling and shutdown also, no luck. He'll run and try it throughout the day, both running and after runs, still not able to get it firm. Now the last two times out after driving home (about 45 minute trip home) he's gone out to try to diagnose the problem and he's then able to prime the bulb. Before he goes out the next time he's gonna try to prime it before he leaves the garage... Dan

  7. Member
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    #7
    factory merc bulb???? hold vertical where check valves can open and close
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #8
    The bulb is also directional, make sure it’s installed in the right direction.
    Mercury 2002 200hp Carbed Saltwater
    OT566776
    2002 Cape Horn 22' Bay

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    #9
    Yes, Mercury bulb... First thing I checked was the Arrow... Like I said, last 2 times out once he backs it in the garage chocks the tires, he says the primer bulb has gotten firm... Thanks guys... Dan

  10. Member lpugh's Avatar
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    #10
    Could be a partial vapor lock problem, The bulb nor the pulse pump will move vapors very well. If the vst is full and the needle valve is close (not allowing fuel or vapor to pass) and there is vapor in the bulb or line going to the pump the bulb will not firm up because the vapor bubbles can not be purged due to the closed needle valve. When the temps of the fuel and vapor in the lines and bulb drop much of it can now return to liquid form which is solid under pressure which means the bulb will firm up, vapors are easily compressed and would not allow the bulb to get firm. Take following a steps to eliminate this possible cause

    Top brand, top tier fuel
    Bulb mounted arrow pointed up no more than a 45 degree angle, this allows for better purging of vapors and vapors will not get trapped in it
    Shorten line if possible and be sure there are no low spots which can trap vapors
    Try to keep the line going uphill all the way to the VST as much as possible
    Use only a Mercury Bulb
    No additional filters or water separator of any kind
    Check the pick tube in the tank for any form of restriction
    inspect or replace all fuel line, quite often they are restricted internally and this can cause the fuel to change to a vapor due to increased vacuum (low pressure)
    If there is a check valve in the fuel pick up, be sure it is free and unobstructed, I do not feel they are needed in most cases since the bulb serves that function as well

    Google
    Vapor Lock and Reid Vapor Pressure
    for more on this subject
    Last edited by lpugh; 07-19-2019 at 07:25 PM.
    Thank You Leon Pugh

  11. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #11
    Have him rotate the bulb so that the arrow points SKYWARD when pumping the bulb. See if it gets hard then (this is the norm... can lay in any orientation AFTER it's pumped firm).

    If it does not, it is likely that there is an air leak somewhere between the fuel level (in the tank) and the bulb. Other possibility is a collapsing hose.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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