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changing lower gear case oil

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  • changing lower gear case oil

    is there any difference in 90 weight gear oils? does it have to be marine stuff like 'lubrimatic' or just plain old 90 Castrol? last thing. is it recommended to flush and drain the gear case with mineral spirits or something to de-gunk it?thanks

  • #2
    Re: changing lower gear case oil

    Use outboard gear oil. If its not all gunked up and crappy just drain well and refill using the drain hole to fill Till it comes out vent hole.


    • #3
      Re: changing lower gear case oil

      I drained it today and to me it was pretty dirty. When I filled it a little black sediment was pushed out and then ok. I think I'll run it a few times then replace it to be sure.


      • #4
        Re: changing lower gear case oil

        J140,Use NEW gaskets (O rings) on the fill and drain screws!!! Buy them from a marine dealer that handles your type of engine. They're CHEAP! and cheap insurance!


        • #5
          Re: changing lower gear case oil

          What is the easiest and cleanest way to perform this task? Every time I squirt gearcase oil into the fill hole in my 15 hp Merc, the oil starts draining out before I can screw in the vent plug.


          • #6
            Re: changing lower gear case oil

            Easy to change. Take the drain and fill plugs out and let drain to a oil pan. Put new seals on both plugs. Buy one of the oil pumps that screws right on top of outboard gear oil. Screw the tube from the pump right into drain hole. Pump until oil comes out fill hole. Put in fill plug and thighten. Remove Pump tube and screw in drain plug.
            Have some fun and enjoy the Great Outdoors.
            Love to fish out of Bodega Bay, California.


            • #7
              Re: changing lower gear case oil

              All you have to do when the lower unit is full is to put the VENT plug in first before you remove whatever your using to fill the unit with...You'll only lose a drop or two.


              • #8
                Re: changing lower gear case oil

                just as an aside...I once look at the spec. sheet for Lubrimatic marine lower unit oil and a standard Lubrimatic 90 wt. oil. The spec. were identical! Secondly when filling lower unit always fill from the bottom hole and let the oil be forced out the top. TO DO THE REVERSE IS A DISASTER. Put the top plug in first. You lose very little oil when you then put in the bottom plug. If the oil is milky, you have water in it. Besure to change before winter or it will crack the gear case housing. A last point...if you do crack the lower unit, try repairing with epoxy, works great if cleaned properly. A lot easier and cheaper that welding. Just a thought.