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  1. #1
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    2010 Mercury 150 Pro XS - Oil leaks

    2010 Mercury 150 Pro XS - S/N 1B804717

    1 - the black plastic screw on the onboard reservoir cap has loosened up the last 2X. The 2nd time I tightened with pliers (after completing the filling sequence) and it still loosened during the day. No noticeable oil behind boat....but when I tilted it up at the launch, lots of 2 stroke oil draining down from motor. Definitely not stripped....but definitely loosening.

    2 - there appears to be a leak at the nut at the bottom of this "brass" colored fitting where the oil hose goes into....and the 6 oil hoses go to the cylinders. What is this "brass" part called?


    What are the thoughts on why I might be seeing leaks at both places?


    What should I do?
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  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #2
    Entirely possible to see leaks at BOTH locations. The second part is called the OIL PUMP.

    On the engine mounted tank: I've seen that there are some aluminum caps being sold to address this. Honestly something to look at if that's the only problem with the tank.

    Oil pump: REPLACE if oil present at the bottom allen-head screw holding the cover on. An oil pump prime must be completed after oil pump replacement.


    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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    #3
    Thank you. The boat / motor is up at my parents, and my dad let me know the part is leaking.....and I knew it was connected to the oil lines. But after looking for 30 minutes on all the part diagrams I couldn't find it. Why they would put the oil pump on the air handler components is well.....questionable. But since everyone under the sun has had issues with this oil pump means that everyone else has had the same pain as me.

    I probably will take it in to the dealer and have them do it....hopefully they can find the pump quickly.

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    #4
    Well....as usual all dealers (3) within 60 miles are 3-4 weeks out as usual to even take a look at it.

    So I made the drive up to take a look at the motor....

    1) There is oil in the lower cowling from all the leaking.......and some on the electrical connection on the oil pump. But no visible oil anywhere on the pump or hoses on that side of the engine. Not sure where the oil on the electrical connector would come from though.

    2) The cap did indeed loosen on its own the last 2 times out.

    3) The Oil reservoir low oil vent (424254) .....aka the brass T connector is also leaking when the motor is running and filling the onboard oil reservoir.


    Obviously I will replace the T connector....but why would it leak? What is the theory on how everything works in this system?

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    #5
    To add some further details....


    The T connector leaks while the tank is filling with the motor on and the oil tank cap loosened - aka the procedure to fill the oil tank. It is not dripping....it is oozing out. Note that the tank is indeed filling while the check valve is also leaking.....so there is not a complete blockage after the fitting.


    It stops leaking a little after shutting the motor off.
    Last edited by crawlerHarness; 10-17-2022 at 08:31 AM.

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    #6
    I have it figured out mentally. The check valve is stuck open permanently. It only leaks a little bit after turning off because only the hose and a 1/2" on the top of the onboard reservoir is leaking out. Unless I tilt the engine....then more leaks out.

    I will report back after I replace the T fitting check valve later today.

  7. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #7
    The "tee" check valve is normally CLOSED on the small (open) fitting. That fitting opens in the event of an oil RESTRICTION (plugged pickup screen, pinched line, etc) so as to allow air to enter so that the oil in the engine-mounted tank can be consumed without coming under a VACUUM.

    Obviously replace it.

    Oil leak at electrical connector on oil pump: There are three (3) allen head cap screws that retain the stainless endcap on the oil pump. As suggested earlier- check the BOTTOM allen head capscrew. If there's a drop of oil on it, the pump is leaking. Most leaks are from the stainless end (leaks on the other side are usually hose connection 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).
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    #8
    Thank you Europe. I keep checking the oil pump for any signs of oil.....and nothing yet after idling. Obviously there is a lot of oil in the lower cowling from all the leaking. So maybe that is why some got on the oil pump electrical connector which is below the pump....but that doesn't make sense.

    We did change the T connector....and the leak is gone after idling in the driveway. We will test it again towards the end of the week.

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    #9
    Update - After cleaning the electrical connector below the oil pump completely again.....we went out fishing again.

    Came back and saw blue oil on the electrical connector again.

    So had to replace the oil pump ourselves since the marina's are ALL 4-6 weeks out still, and then had the marina we bought the pump from do the priming sequence - quick job in the morning).

    Will keep an eye on everything going forward.

    An interesting note....I asked the mechanic Brad how long can a cylinder go without oil. He indicated "not very long" at WOT. But at idling to 3000 rpms.....you might have longer than you think. He referenced the the E-Tec's that have gone 8+ hours without oil in the cylinders....and no evidence of damage to them. So the biggest worry he has is when you run at WOT.

    He said this ProXS 2 stroke is a great engine....just don't ignore it when it bogs down....even when it goes away. Address the issue.
    Last edited by crawlerHarness; 11-07-2022 at 10:26 AM.

  10. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #10
    And as far as the lubrication situation is concerned... you'll not run your engine for 4 hrs without lubrication in the cylinders (without damage). I'm honestly not buying any 2-stroke making it for very long that way.

    Glad you got it addressed.


    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