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  1. #1
    Petty Officer 2nd Class
    Join Date
    Jul 2006
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    Alabama
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    197

    Default mercury newbie, lower unit gear lube change?

    OK the last three motors I have owned have been Johnsons...this is my first Merc ('98 90ELPTO 2 stroke) so I am learning the differences.
    I just drained and filled my lower unit. After getting the plugs back in I noticed there was a 3rd plug labled "vent". I had only removed the bottom fill plug and the oil "level" plug. On my Johnson motors, the "vent" and "level" plug were the same one so essentially on the older Johnsons there are only 2 plugs as opposed to this Merc with three. I basically did the change the same way I did my Johnson mortors; removed the fill plug, removed the level plug, let it drain and drip, screwed in the oil pump (to the bottom fill hole), pumped it up till oil ran out of the level plug, installed the "level" plug, removed the pump and installed the fill plug...I am waiting on my manual but in the mean time I guess i need to know if I need to go back and re-do anything a certain way using that vent plug? Better safe than screwed I guess...thanks

  2. #2
    Cadet
    Join Date
    Oct 2005
    Location
    On beautiful Lake Winnebago
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    16

    Default Re: mercury newbie, lower unit gear lube change?

    According to the Mercury service manual.

    To refill the gearcase;

    With the outboard in the vertical position, add lubricant until it appears in the front vent hole and install the plug with sealing washer. Continue adding lubricant until it appears in the rear vent hole. Stop adding lube and install the rear vent plug and sealing washer before removing the fill tube. Remove tube and replace the fill plug and sealing washer.

  3. #3
    Petty Officer 2nd Class
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    Alabama
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    197

    Default Re: mercury newbie, lower unit gear lube change?

    done...thanks

  4. #4
    Petty Officer 3rd Class
    Join Date
    Mar 2009
    Posts
    84

    Default Re: mercury newbie, lower unit gear lube change?

    The flush screw is for the water pump and I believe used in salt water applications to flush the engine with fresh water after use. I've only operated OBs in fresh water so I have never had a reason to use it. I think most salt water users just use the muffs so it's kind of a duncil.

  5. #5
    Cadet
    Join Date
    Oct 2005
    Location
    On beautiful Lake Winnebago
    Posts
    16

    Default Re: mercury newbie, lower unit gear lube change?

    Starppy, the screw in question is a vent screw. Mercury has not used the flush screw as you describe in several years for the reasons you stated.

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