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Thread: changing gear oil and seals

  1. #1
    Join Date
    Aug 2004
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    Default changing gear oil and seals

    Guys,

    I walked passed my boat this morning and I noticed that "oil" is leaking out of the bottom bolt of the lower unit on my 2000 Yamaha 40hp 2 stroke. I'm assuming I just need to replace the seals and change the gear oil, any ideas before I take this to the marina and it costs me a small fortune to get it fixed.

    Is this something that I can do myself?

    Help a brother out!!!!!!!!

  2. #2
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    Sep 2008
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    I have never worked on a yammie, but some seals you can do...some seals you have to have the tools to do it with or risk messing something up.

    Before I did anything I would drain the fluid and see if it has any water intrusion. Oil leaking from back there can come from the powerhead...as the exhaust runs through there...in winter we lower the engine down and sometimes oil or fuel oil can leach its way down through the exhaust picking up gunk on its way and when it exits it looks like LU lube.

    If your lube is pastey white...you have a problem. If you drain it and its clean...replace to the little orings under the drain and vent screws and don't worry about it. If it is lube, and its dripping, you have a good leak..normally we do not see lube dripping like that...normally you'll just find white pastey looking lube. The viscocity of water is way less than oil and the LU can actually hold a vaccuum while you are running due to everything moving inside. Much easier for water to get in than oil get out.

    Check the fluid...if white, take the lower unit off and have it psi tested and vaccuum tested. Shops should do this cheap if you take the unit to them. If you can, go with them and see where the bubbles come out. If its a seal that you can replace, replace it. If not let them just put new seals in it.

    Something else you can do...go to the parts department at your shop and have them print you out an exploded diagram of your LU. They have all this on computer. Look it over. You might see that you can do it yourself.

    If you decide to take it in...take the lower off and take it in. That will save you probably an hour labor charge. I would do water pump impellor too while I was in there. Just some thoughts. I'm a penny pincher...lol :D
    "But if serving the Lord seems undesirable to you, then choose for yourselves this day whom you will serve, whether the gods your ancestors served beyond the Euphrates, or the gods of the Amorites, in whose land you are living. But as for me and my household, we will serve the Lord. Joshua 25:15

  3. #3
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    reread your post....what bolt/screw are you talking about? If its the drain plug, just drain the fluid, replace o-ring or washers in the drain and vent and you should be fixed. Yes, you can do that.
    "But if serving the Lord seems undesirable to you, then choose for yourselves this day whom you will serve, whether the gods your ancestors served beyond the Euphrates, or the gods of the Amorites, in whose land you are living. But as for me and my household, we will serve the Lord. Joshua 25:15

  4. #4
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    What Scrapper said. Drain it, flush it from the top with a bottle of lube, replace gaskets on plugs and refill. No need to flush it if it is not milky.

  5. #5
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    Sounds like all I need to do is remove the drain plug and refill. I read somewhere that I have to fill it from the bottom. Is that true, or do I just drain it, put the bottom plug/bolt back in and refill?

    Thanks for all the help!!

  6. #6
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    There should be a vent on top of the lower unit...you unplug it...then the drain plug. Let it drain out...if clean and not milky, just stick your gear lube pump....go ahead and buy the little pump...makes it WAY easier...and pump until it comes out of the top plug. Have the bottom plug ready and pull the pump insert out and put the new washer/oring and plug back in. If you try to put it in from the top air pockets will occur and it won't get full. Fill from bottom, when it comes out of the top hole, your done.
    "But if serving the Lord seems undesirable to you, then choose for yourselves this day whom you will serve, whether the gods your ancestors served beyond the Euphrates, or the gods of the Amorites, in whose land you are living. But as for me and my household, we will serve the Lord. Joshua 25:15

  7. #7
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    What Scrapper said. I put the top plug in first too reduce the flow out the bottom.

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