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  1. #1

    Default NS8B lower unit questions

    I'm taking apart a 8HP NS8B two stroke lower unit since I found milky gear oil. I managed to pull the bearing carrier and prop shaft out but I'm stumped on how to pull out the driveshaft. The service manual says to use a special splined tool on the driveshaft to spin off a pinion gear retaining nut, but I don't see a retaining nut, seems to me like the driveshaft is just held in place with an interference fit on the caged ball bearing mated to the gearcase body in pic 2. If so, how does one press out/pull out the bearing to replace it?

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  2. #2
    Join Date
    Dec 2020
    Location
    Central Pennsylvania
    Posts
    11

    Default Re: NS8B lower unit questions

    It almost looks like there was something out of kilter and the flats were ground off the nut There are markings on the gear teeth that match the edge of the nut. Were there metal shavings in the oil?

  3. #3

    Default Re: NS8B lower unit questions

    Quote Originally Posted by ddc11 View Post
    It almost looks like there was something out of kilter and the flats were ground off the nut There are markings on the gear teeth that match the edge of the nut. Were there metal shavings in the oil?
    No shavings or metal debris in the oil, the gears look pristine. I do not believe there was a nut ever in the first place as the pinion gear looks pressed on to the end of the drive shaft splines. See attached pic for a close up shot.
    Click image for larger version. 

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    I'm wondering if there are any good ways to pull out the driveshaft, my initial thought is to use something like this just clamped on the shaft end:
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  4. #4
    Join Date
    Dec 2020
    Location
    Central Pennsylvania
    Posts
    11

    Default Re: NS8B lower unit questions

    Looked closer and what I thought was wear must of been light reflecting from the camera. Never had one apart but the pictures and diagrams in my manual all show a nut. It is a mystery to me too,

  5. #5
    Join Date
    Dec 2020
    Location
    Central Pennsylvania
    Posts
    11

    Default Re: NS8B lower unit questions

    I do not claim to have much knowledge of these motors as I have just acquired my first one a few months ago. I did download and print the manual from Tohatsu and find some things are not really clear and may lose it in interpretation. Looked for images for the drive shaft on the net and found this picture and it has no threads for a nut. Hope that someone with knowledge chimes in and help with your motor and my curiosity as to the procedure for taking it apart.Click image for larger version. 

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  6. #6
    Join Date
    Mar 2010
    Location
    Hamburg, NY, USA
    Posts
    3,142

    Default Re: NS8B lower unit questions

    There is no nut. Pull out the driveshaft with the bearing still attached and you are all set. Sometimes, a good tug with a gloved hand will get it out.
    Paul
    Certified Tohatsu TLDI Technician
    Hamburg, NY USA

  7. #7

    Default Re: NS8B lower unit questions

    Quote Originally Posted by pvanv View Post
    There is no nut. Pull out the driveshaft with the bearing still attached and you are all set. Sometimes, a good tug with a gloved hand will get it out.
    Thanks for your responses guys. Following Paul's advice, I was able to pop out the driveshaft by clamping it in a vice and beating on the housing with a rubber mallet to dislodge the bearing. Bearing was sealed in there with accumulated crud.

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