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2001 150 HPDI Do the lower unit seals need replaced?

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  • 2001 150 HPDI Do the lower unit seals need replaced?

    In the process of installing a water pump this spring, I noticed that there is some lower unit lube leaking up into the water pump housing. Doesn't seem to be a lot but that is clearly what it is.
    I regularly check the gear case lube and have seen no signs of water. No milky lube in the gear box, no separated water visible when I change the lube.
    It has been a while since I've done the water pump myself, but I don't recall seeing signs of lube in there. My better judgment tells me it is time to ask some experts before proceeding with this project.
    Do I potentially have the early stages of an upper seal failure in process?
    Should I forget the water pump project and get the lower unit serviced, seals replaced, etc?
    Or, could I reasonable expect to operate through another Michigan season while keeping a careful eye on the lower unit lube?

  • #2
    You are likely OK for the season.

    The seals are positioned to keep water out.

    There are two stacked seals at the input drive shaft under the impeller and another double stack set at the propeller shaft. They are orientated in such a way so as to keep raw water out.
    When i was younger and working OMC, they used to stack them so the one faced the gear oil and the other faced the sea water. Yamaha does it different with both seals facing the seawater.

    Now, they are 20 years old... You are right there, and it is only four bolts if I remember correctly. Most parts house will have them on the shelf for $8 each...

    The test is to apply 14 PSI shop air pressure with the gear oil drained and see if it holds for a period of time.
    If its got teats or tires, you bound to have trouble with it....


    • #3
      I got to thinking about the oil around the water pump while i was riding around cutting the grass...I'm wondering if that could possibly be oil that had run down the inside of the motor from the 2 cycle reservoir. I started having the issue where the oil reservoir leaks when the motor is tilted all the way up this past year. Upon closer inspection, the oil at the water pump looks more like the dark green/blue 2 cycle than the lube in the lower unit. Any thoughts on the likelihood of that being the case? I keep trying to understand how I could have bad seals and no sign of the lower unit lube being contaminated. If that 2 cycle that was draining into the engine compartment could make its way down to the water pump chamber, that might explain what is going on.


      • #4
        easy to tell the difference,
        lower unit lube stinks a lot more than 2 stroke oil.
        just touch your finger to the oil and then sniff it


        • #5
          The sniff test indicates that the oil is 2 cycle. The color also pointed to 2 cycle. I use a synthetic that is gold/brown. The oil at the water pump definitely had the blue/green tint of the 2 cycle I use.


          • #6
            well now you have a different leak to find a fix for


            • #7
              I've used the Quick Silver lower unit oil, it is blue in color too. So the sniff test (or taste) is the only way to discern.

              That engine oil reservoir tank cap/level sensor leak is common. Try a ty-wrap around the rubber lip. That has worked for me.
              Also, clean that oil off of your cowl seal, it makes it all gummy and easily damaged. I used plain ole 'Blue Dawn' dish detergent and did it again the next week. Repeat as needed, it will eventually get better, I promise. If Blue Dawn is gentle enough for baby ducks in New Orleans....
              Last edited by FabricGATOR; 05-17-2019, 10:15 AM. Reason: removed profanity for family church viewing...
              If its got teats or tires, you bound to have trouble with it....