Reply To: 1947 HD-25 Water Pump and Lower Unit oil

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April 27, 2026 at 1:02 am #316599
Sam M.
Participant

    Canada Member
    Sam M. wrote:

    There is an AOMCI thread about gear grease vs oil that describes this, but I can’t seem to find it at the moment.

    Found it!

    https://www.aomci.org/forums/topic/john-deer-corn-head-grease/

    Look at Mumbles’ comment on page 2.

    And take a look at the 90 wt. vs SAE 40 being discussed here:

    https://www.aomci.org/forums/topic/td-20-lower-unit-lube/

    Finding a manual for your motor should clear up the reccomended oil weight for your specific gearcase.

    Another thing to think about is that you can find 90 weight marine gear oil (designed for outboard gearcases) that is intended to deal with water intrusion.  Not sure about finding an SAE 40 oil that can do that.