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  1. #1
    Member
    Join Date
    May 2014
    Location
    Louisville, Ky
    Posts
    243

    Yamaha HPDI lower unit

    Question have a 225 HPDI wanted to
    change lower unit oil pulled the plug and nothing but water came out very little oil. I know I need to put new seals in the lower now! Question my motor hasn’t been turning the rpms it should and I’m sure it’s not a power head issue or prop issue. Could the lower unit cause the power loss due to friction in the gear case. It would only turn 5500 rpm with a 25p prop on a 20ft boat.

  2. Moderator 21XDC's Avatar
    Join Date
    Sep 2004
    Location
    Westland Michigan
    Posts
    63,353
    #2
    Water turns easier than oil.

    Marks Props 317-398-9294, 1850 East 225 South, Shelbyville, Indiana 46176 propellerman59@gmail.com http://www.marksprops.com/index.html

  3. Member
    Join Date
    Jul 2014
    Location
    Toledo Bend Tx
    Posts
    485
    #3
    Yes, the lower can cause a lose in RPM's. You may have a bearing seizing up due to the water.
    If you are going to have a mechanic do the seals, you might as well have it taken down and inspected.If they know what they are doing, they can have it totally dis-assembled in about 30-40 minutes.
    That would be cheap insurance vs having it come apart while running.

    FYI. HPDI's weep LU oil and should be checked and topped off periodically if they are run often.

  4. Member
    Join Date
    Apr 2015
    Location
    ponchatoula la
    Posts
    1,490
    #4
    Seems my ox66 does too about 4 ounces every 4 hrs run time. With new seals

  5. Member
    Join Date
    May 2019
    Location
    Kansas
    Posts
    30
    #5
    Never a truer statement has been uttered. I have no idea how mine did that but NEVER had any water in there. I changed lower unit oil about every 50 hours of engine run time just for good measure. Oil is cheaper than iron and aluminum

    Quote Originally Posted by 21XDC View Post
    Water turns easier than oil.