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A new problem/lower unit

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  • A new problem/lower unit

    Hello everyone, I have a 1992 Yamaha 40 MSHQ. I bought the boat and outboard for a project 3 years ago. Got the motor running carburetors etc. Just finished a rebuild phase on the boat so I could do some fishing.

    Everything has been great. Able to count on the outboard and really liking the way I put the boat together. Meanwhile keeping up with all the preventative maintenance which I’m adamant about.

    Today I cleaned the power head and detailed it. It needed to be flushed also. So I ran it in a big drum I’ve cut down to size. It gets way better water pressure than with muffs and I keep the fw hose continuously running keeping fresh water in the barrel. So I ran it about 5-10 minutes. Never any longer. I use the boat in freshwater only by the way.

    After removing the drum I was wiping it down and saw what’s in the picture here. It was late so I’ll pull the prop tomorrow but I’m pretty sure my seals behind the prop are gone.

    Ill know for sure after pulling the prop and draining the gear case. I just changed it a month ago and always use new OEM gaskets on the top and bottom plugs.

    Can someone give me an opinion because it looks more like mud than oil with water in it? It’s coming from between the prop and case.
    Once again I’ll be entering new territory changing out the seals. I would greatly appreciate any knowledge shared that may help me. I’m wanting to get it done and get back on the water.
    We are having a church picnic at the lake this weekend and I’m supposed to give boat rides.

  • #2
    Mud will have a completely different "feel" to it than oil. But based on that color, it could just as easily be oil/water (a milkshake).

    Not sure I can say anymore - at least not definitively. Pull the prop and check it out - pressure test.
    2000 Yamaha OX66 250HP SX250TXRY 61AX103847T
    1982 Grady Weekender/Offshore (removed stern drive & modded to be an OB)


    • #3
      I pulled the prop and cleaned around the seal. I’ll post pictures. Maybe it’s me but I think I see a small gap between the seal and prop shaft.

      As for the sludge in my first picture I figured out it’s un burnt 2 cycle mix. To begin with I have and old style portable fuel tank so when I store it I have to leave tho vent open. I usually add some fresh mix before each trip but I’m trying to run the tank low because I have a new one to try. The last three trips have been no telling how much gas evaporated leaving it a rich mix.
      Then the last trip was at night and I did all idling and never opened it up. I noticed it smoked way more than usual. Duh.

      I drained the lower unit and it looks like it did the day I put it in there 3 months ago accept it looked like it had a little water. But I noticed water dripping in the pan that was from me moving the motor up and down. I refilled with gear lube. Even if it is leaking somewhere I want to keep lube in the case until I can do something.
      I want to get a tool to pressure test.
      Does anyone have any recommendations that won’t break the bank?