Bottom end oil…….& water

2008 Mercury 50hp 4-stroke, bought fall 2018, not sure when the impeller was last done, I keep a close eye in on the tell-take stream and for sure going to have it done next year

The main reason behind checking/changing the Lower End gear oil is to make sure there is no water in it. If it's milky ... change it ! The possibility of water being in the Hub and freezing may cause blown seals or even cracking of the Lower Unit. Just like fogging the engine or adding a stabilizer to the fuel check or change the Lower Units oil is standard procedure in my book. Needless to say if it's a 4 stroke to also change the engine oil.

As for water pumps ? Cheaper to change them then blow your motor ! I've seen some with their "pisser" working fine at idle but once you throttle up it reduces to a trickle or nothing at all; this could indicate your vanes on the impeller have worn down too much which causes it not to seal against the pump housing causing lack of flow causing the motor to over heat.

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Originally Posted by 73hunter

So, a rainy day before storing it away for the winter is a great time to change the bottom end oil…..

pulled the bottom drain screw out and I got a little water, not much more than a capful, and quite clear…pulled the top vent screw out and out came the oil….beautifully golden. Boat has sat for a week since last use.

so….is a little water like that something that warrants a look at seals or does everybody get it ?

Other years some of the oil has been black as midnight, but no water

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If the water is not mixed in with the oil, and it sounds like it is not, then it did not occur from running the motor. A small amount that you describe could be condensation build up.

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Originally Posted by Marker

If the water is not mixed in with the oil, and it sounds like it is not, then it did not occur from running the motor. A small amount that you describe could be condensation build up.

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That’s kind of what I figured. Going to take it for service in early spring to have the all lower end seals replaced so I know it’s done. Put some new oil back in for the winter anyway.