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  1. #1
    Petty Officer 1st Class msd58's Avatar
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    Default 90 Yamaha 1997 Lower Unit Question

    RE: DRAINING AND REFILLING LOWER UNITI followed the draining a refilling procedure properly at first. Cracked open vent screw, drained oil out bottom, refilled until gear lube and bubbles came out vent hole. I tightened up on vent screw. I must have gotten distracted by a cell phone and accidentally pumped a little more and saw some weeping of new oil out of the water pickup vent on lower unit. Do I now have problem ?

  2. #2
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    Default Re: 90 Yamaha 1997 Lower Unit Question

    hello where in any service manual did you find "crack the vent screw". so your statements are contradicting. did you have the screw still in as you filled it from the bottom? if so its remotly possible to have damaged the driveshaft seals. drain it properly and have it pressure tested or just double check that it is full and check the oil condition after each outing. be aware that the drain/vent gaskets are not lifetime units and replace them when they start looking deformed. good luck keep posting and get a better manual
    no tech questions by PM, they wont get answered.
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  3. #3
    Petty Officer 1st Class msd58's Avatar
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    Default Re: 90 Yamaha 1997 Lower Unit Question

    What I meant was I opened it up. Sorry

  4. #4
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    Default Re: 90 Yamaha 1997 Lower Unit Question

    hello did you open it or remove it? all the manuals say remove it. anyway the seals on that yammi are set with all seal lips facing out. your gear case should hold about 14 psi when new. I will accept 10-11 psi used.sometimes you can push the seals out if using a hand pump that threads in the case with the vent screw in place. normaly it will push the shift shaft seal out but it can force oil past the drive shaft seals. now you have to think" do I feel lucky" if ya do, run it. if ya dont the unit will need to be drained and pressure tested. good luck and keep posting and dont shortcut the manuals
    no tech questions by PM, they wont get answered.
    you have to be trusted by the people that you lie to .

  5. #5
    Petty Officer 1st Class msd58's Avatar
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    Default Re: 90 Yamaha 1997 Lower Unit Question

    Thanks for your prompt attention. I was using hand pump. I did run the motor with hose for a while. I checked for any additional weeping. There was none. Do you think its possible that the water pump seal is damaged?I feel pretty stupid

  6. #6
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    Default Re: 90 Yamaha 1997 Lower Unit Question

    hello I have seen this done before. some engines continued to leak and others did not. if you cannot get the unit tested then run it a few hours and then "crack" the drain plug and look for milky oil. if no milk then keep running but continue checking. if in 2 or 3 runs no milk is present then I would think its ok. otherwise putting drive shaft seals in that motor is not a very big deal if all the bolts come out. good luck and keep posting but trust me you cannot do anyworse than I ever did I just happen to have made most my mistakes as a teen some years back and I am smart enough to cover them now
    no tech questions by PM, they wont get answered.
    you have to be trusted by the people that you lie to .

  7. #7
    Petty Officer 1st Class msd58's Avatar
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    Default Re: 90 Yamaha 1997 Lower Unit Question

    If I have to pull the lower unit; I never done a Yamaha before. Mercurys and Mercruisers. Is there anything special?

  8. #8
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    Default Re: 90 Yamaha 1997 Lower Unit Question

    hello about the same as a merc only easier. just remember the speedo pitot tube from the gearcase if used on your model. if you have ever changed a merc water pump its easier on a yamaha if the bolts come loose. good luck and keep posting
    no tech questions by PM, they wont get answered.
    you have to be trusted by the people that you lie to .

  9. #9
    Petty Officer 1st Class msd58's Avatar
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    Default Re: 90 Yamaha 1997 Lower Unit Question

    I just looked at it. Yes, Its easy as you said. Is the bolt inside that holds the trim tab/anode metric? My 1/2" felt a little sloppy and its not 7/16". I might pull it tomorrow too stormy today. had to get out of the rain.PS I saw no signs of oil anywhere. Clean.

  10. #10
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    Default Re: 90 Yamaha 1997 Lower Unit Question

    everything on a yamaha is metric you will need a 12mm socket a 10mm socet and a 14mm wrench maybe a 13mm wrench. I am old and cant remember everything
    no tech questions by PM, they wont get answered.
    you have to be trusted by the people that you lie to .

  11. #11
    Petty Officer 1st Class msd58's Avatar
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    Default Re: 90 Yamaha 1997 Lower Unit Question

    Thanks. Do I leave in gear or neutral? Are you the moderator for this site?

  12. #12
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    Default Re: 90 Yamaha 1997 Lower Unit Question

    hahahaah heck no I cant even keep my kids from arguing. I spent way to much time in the navy to volunteer for that spot. I just have some severe joint problems so sometimes I sit here and postulate. . the navy retired me for them in 95 so I went back to work with a tool box. however I have wrenched for almost 30 years . leave it in nuetral. works just fine. will be easier to take it someplace and have it pressure tested. but chaning the seals for the drive and shift shafts is easy. good luck and keep posting
    no tech questions by PM, they wont get answered.
    you have to be trusted by the people that you lie to .

  13. #13
    Petty Officer 1st Class msd58's Avatar
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    Default Re: 90 Yamaha 1997 Lower Unit Question

    Thanks I'll let you know how I make out

  14. #14
    Petty Officer 1st Class msd58's Avatar
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    Default Re: 90 Yamaha 1997 Lower Unit Question

    Pressure test failed. It seems to leaking out through or underneath water pump seal. I'll keep you posted.

  15. #15
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    Default Re: 90 Yamaha 1997 Lower Unit Question

    I know this is an old post but I.m hoping you guys can help me. I have an 89 Yammy 90HP. I want to change the lower end lube but I only have one oil screw. Its labled oil level. My Johnson had two, one lower than the other, so you could pump it in the lower hole and the air comes out the top one. How do I get oil in their without air bubbles too? They have no place to go without a vent screw to open.
    Just when you think you know all the answers to all the questions........they change the questions!!!

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