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  1. Member
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    #41
    whats inside the 90 degree fitting that the vent hose is connected to? Screen? Valve?

  2. Member
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    #42
    possible screen or dirt dobber
    .................................................. ...the scariest thing in life is the unknown ...................................

  3. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #43
    Your latest problem descriptions are clearly leading to and indicating an inability of the FUEL PUMP (pulse fuel pump) to pump fuel into the VST. There are only so many possible causes for this, below are a few:

    -Pulse Pump needs to be rebuilt, OR if it has been, something was not done CORRECTLY (warped check valves, loose check valves, incorrectly stacked gaskets/diaphrams, springs/caps in wrong place or orientation, etc.

    -Broken or damaged reed on one or more cylinders

    -Fuel line between bulb and fuel pump compromised (inner liner folded up during install)

    -Loss of compression on one or more cylinders.

    Did you perform every item recommended on Page-1 of this thread, under "Fuel Lines and Performance Problems"?


    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

  4. Member
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    #44
    I just went back and re read the fuel line process. Everything was done. Parts were all Mercury/Quicksilver except fuel line. What are you calling the pulse pump? The only thing I rebuilt on the VST was the diaphragm as recommended. Those parts that came out looked to be in good shape. There was no trash inside or pinholes anywhere in the old stuff.

    To me it seems like the problem is between the tank and the motor. I will upload a video later showing the motor running at different speeds.

    Thanks for the replys.

    I can check the compression. I will search for specifics on checking optimax compression.

    Also as a side note... it's still taking 15 to 22 pumps to fill the primer bulb/fuel system when it runs out. The tank is full. That just doesn't seem normal.
    Last edited by OldDude7; 04-01-2021 at 10:23 AM.

  5. Member
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    #45
    I pulled the vent hose this morning. It was routed flat across the top of the tank to the filler neck with no visible way for it to hold fuel. When I removed it a lot of gas came out. It was nasty looking. Maybe that was blocking the vent? Shouldn't the venting device not allow fuel to go thru the like like that? The attached pic is of the fitting the vent hose was attached to.
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  6. Member
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    #46
    Vent wasn't the problem. Died again about 23 minutes into running. Re-primed the bulb. Ran another 10 min this time then died again.

    I uploaded some videos to YouTube. If I can post links here I will so you can see and hear what its doing.

    Thought is to try a dummy tank or clear fuel line.

    DO they make a scanner for the electronics for this engine? If so any recommendations? Im thinking its cheaper to do that than it is to start replacing parts until something fixes it.

  7. Member
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    #47
    Here are the video links.








  8. Member
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    #48
    Have you ever tried running this engine off a known good portable tank? If not, try it, should help isolate whether it's engine or boat side.
    _______

    Phil
    '09 Hewescraft ProV
    '09 150 Optimax


  9. Member
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    #49
    i would try test with another line and tank on lake not good to run it like that no load on gearcase may loose gearcase , also see if you can mount fuel line where bulb holds vertical check valves work better that way, would also disassemble pulse pump again lets make sure its right its running out of fuel alright possible something in tank getting sucked over pickup hole , need to eliminate tank and line as possibility
    .................................................. ...the scariest thing in life is the unknown ...................................

  10. Member
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    #50
    @SilverFox579... the portable can is my next test. My neighbor suggested trying a clear fuel hose to se If it's pulling air thru the fuel line somehow.

    @Joe54... did you mean mounting the primer bulb vertically? Also can I disassemble the pulse pump without needing new gaskets again? Thanks for the pointer on running with no load. My local guy said it was ok as long as the water pressure thru the motor was good.

    Shouldn't there be a vacuum in the fuel tank end of the hose? If so any idea what it should be?

    Also I just spent an hour searching for the proper way to check the compression and what it should be. I am assuming warm engine 90 to 115 psi with no more than 15psi variance between cylinders from what I read. is just pulling the electrical connectors from the coils sufficient to check compression?
    Last edited by OldDude7; 04-02-2021 at 02:12 PM.

  11. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #51
    Scanner Question: Diacom Software is relatively reasonable for a DIY user.

    That won't solve THIS problem, however.

    Really shouldn't have any significant vacuum in the line at the tank (no more than 2.5" hg at any RPM) as it indicates a RESTRICTION. That being said- I strongly believe your problem (as stated early on several times) is in the Pulse Fuel Pump, Reeds or lack of compression on the driving cylinders.

    Before wasting a ton of money further:

    Did you use Piping HOT WATER to dip the new (gray) line into for 20 seconds before installing the line on the nipple at each end? If not- check for inner lining folded over at the end of the gray line (both ends).

    Please snap a couple of pictures of the Pulse Fuel Pump and post them. Might not be a bad idea to open it up again just to make sure everything is stacked in the right order, the check valves are not cupped or falling out, all arrows are on the same side of the pump, the diaphrams are at the OUTSIDE, and the mounting gasket is properly installed under the pump.


    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

  12. Member
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    #52
    First off, I am greatly appreciative of everyone's input. I am not trying to come across any way other than grateful. I am thankful these forums exist for guys like me who like to make sure things are done right.

    Quote Originally Posted by EuropeanAM View Post
    That being said- I strongly believe your problem (as stated early on several times) is in the Pulse Fuel Pump,
    Again, is the pulse pump the pump on the from the diaphragm was replaced in?

    Quote Originally Posted by EuropeanAM View Post
    Reeds or lack of compression on the driving cylinders.
    Please correct me if I am wrong...

    My understanding of reeds from working on 2 stroke dirt bikes is that they control the air fuel mixture. I have been working on various types of engines of some sort (excluding marine outboard) all of my life. I assume it is the same in a 2 stroke outboard??? From my experience, when the reeds are bad in a KTM 65SX for example, the bike wouldn't run right, had no power, etc... From the videos I posted, the boat is smooth for the most part (there is a slight shrudder from about 1600 - 2600 rpm) and it is super smooth when running in the power band (3200-5500rpm).

    Also, my understanding regarding engine compression is that it increases and actually stabilizes when the engine is at operating temp.... hence the recommendation for checking the compression with the engine at or as near operating temp as possible. Is their something different in an Optimax? The performance of the engine for roughly 25 minutes before experiencing problems isn't indicative (to me at least) of a compression issue. I don't understand how the problem would become more apparent and even more pronounced as the engine warms.

    Quote Originally Posted by EuropeanAM View Post
    Did you use Piping HOT WATER to dip the new (gray) line into for 20 seconds before installing the line on the nipple at each end? If not- check for inner lining folded over at the end of the gray line (both ends).
    Again, as stated several times, I followed the instructions explicitly. The parts used were Mercury/Quicksilver. Although the pics wouldn't load for me, the written instructions are very well done, simple, and I followed them to the letter. You guys know what you are doing and I don't need or desire to re-invent the wheel.

    Quote Originally Posted by EuropeanAM View Post
    Might not be a bad idea to open it up again just to make sure everything is stacked in the right order, the check valves are not cupped or falling out, all arrows are on the same side of the pump, the diaphrams are at the OUTSIDE, and the mounting gasket is properly installed under the pump.
    I will do this today. I wanted to make sure I dont need a new diaphragm gasket kit. I realize some applications require this and I dont want to make it worse. I will post pics of the pulse pump. I even checked and kept the old parts. There were no pinholes, and all the gaskets are intact except for the one between the pulse pump and the VST.

    Joe54 suggested the primer blub be vertical. Does it matter if the arrow is pointing up or down?

    Again, thank you in advance for your thoughts and explanations.

  13. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #53
    Primer bulb must be able to rotate to have the arrow pointing SKYWARD when you pump the bulb. Once pumped firm, it can then lay in any orientation.

    Pulse pump is the pump with two diaphragms, two gaskets, two check valves with keepers, two springs and two spring stops, as well as a mounting gasket (in the OEM kit). This is the pump that accomplishes moving fuel from the tank pickup into the VST (and for whatever reason it is obviously either not doing it's job or NOT CAPABLE OF doing it's job).

    Reeds act as INTAKE VALVES on the front end of the crankcase. In other words- they should allow air IN, but NOT allow air back out. They do not control fuel mixture (as there is no fuel in the engine at this point... fuel is injected directly into the combustion chamber).

    If a reed does not seal or is broken, there will be a leak in the crankcase through that reed, greatly reducing the alternating pressure and suction that is the force that drives the diaphragm(s) in the pulse fuel pump. Low or no compression on a cylinder could also have a similar result.


    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

  14. Member
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    #54
    Wouldn't bad reeds cause an engine to run bad all the time... not just after 20 to 25 min? Same thought with a bad pulse pump? This isn't a problem that becomes an issue until the boat has been running 20-25 minutes consistently... regardless of on the lake or using muffs.
    Last edited by OldDude7; 04-02-2021 at 08:17 PM.

  15. Member
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    #55
    The pulse pump is the one you rebuilt on the VST and where the fuel line from your tank attaches to the engine.

    For Optimax compression testing see the FAQ at top of either the 2.5L or 3L forums. There is a boatload, pun intended, of useful information in them. Though specifically oriented toward the bigger Optimax engines there's a lot that applies to ALL Optimax engines regardless of displacement.

    What is the part number on your Mercury service manual?

    Compression Testing
    _______

    Phil
    '09 Hewescraft ProV
    '09 150 Optimax


  16. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #56
    Quote Originally Posted by OldDude7 View Post
    Wouldn't bad reeds cause an engine to run bad all the time... not just after 20 to 25 min? Same thought with a bad pulse pump? This isn't a problem that becomes an issue until the boat has been running 20-25 minutes consistently... regardless of on the lake or using muffs.
    If the engine is running out of fuel (which you've proven a number of times now), you must address those potential causes. And either of them are potential causes.

    An air leak upstream of the primer bulb (or pickup tube not below fuel level) are other possible causes.

    Note: Just an FYI: If you pump the bulb up firm, and start the engine on a flush attachment, the engine will run 20-28 minutes at 1500 RPM's or below (on the fuel contained inside the engine's fuel system, even with the fuel line disconnected from the pulse pump).

    In other words- it sounds like the engine is running for about as long as it takes to consume the fuel you have pumped up to it with the primer bulb, and then simply running out of fuel (completely).


    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

  17. Member
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    #57
    @SilverFox579... pic attached of manual. Thanks for clarifying. I was reading it last night. Some things are different, such as VST and location of electric fuel pumps. Some things like the diagram of the use fuel pump internals are the same.

    @EuropeanAM.... if the motor runs at least 20 min one the fuel in the system from the bulb to the engine, then shouldn't it run for the same amount of time everytime the system is primed? It's only running anywhere from 1 to 10 minutes on anybsuslbsequent fuel system primes. I'm working 9n re-doing everything today. I will post pics.
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    Last edited by OldDude7; 04-03-2021 at 10:16 AM.

  18. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #58
    It would depend on the engine RPM's, and on how well you had managed to prime the system.

    Are you somehow thinking the engine is NOT running out of fuel?

    Also: It is never wise to run an engine at more than approximately 1100 RPM's when there is NO LOAD. In several of your videos you had the RPM's pretty high for extended periods, with no load on the engine (this can cause severe internal damage to the engine).


    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

  19. Member
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    #59
    No I think it's running out of fuel. I'm trying to figure the correlation between the engine running for 20 plus minutes a fuel system prime when started from cold and that the system only running for 1 to 10 min on subsequent fuel system primes when the engine is warm with there being no difference in how the engine is run.

    I bought another primer bulb and a diaphragm kit for the pulse pump so as not to take any chances. I'm going to cut 2 inches from the new fuel lines to make sure there isn't a liner problem.

    I simply can't wrap my feeble brain around this issue when it's acting like a simple fuel problem. I should have just bought a new boat.... ��

    Is it possible since the pulse pump runs off the engine compression there could be something obstructing the vacuum tube from the pulse pump to the engine?

    The pic is the diagram I'm using to rebuild the pulse pump
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    Last edited by OldDude7; 04-03-2021 at 12:07 PM.

  20. Member
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    #60
    Pulse pump removed again amd rebuilt again using new parts. Pics below. O rings on brass fitting on top replaced... 2 on one side 1 on the other. Vacuum line to crankcase checked and has no obstructions. Filter removed and checked. No debris noted. Both VST bowls drained and the fuel caught in a clean bowl. Nothing noted in it either. I cut 2 inches off each end of the new (last week) 5/16 fuel line. Heated in 150 degree water for 30 seconds. Reinstalled each end. 4 total. Replaced the primer bulb again.... this time with a 5/16 Atwood. Dealer was out or Quicksilver/Mercury. New clamps on all fittings to alleviate the possibility of a bad clamp.. Will see what happens now....
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