After I put in a new driveshaft on my 73 Evinrude 25 hp outboard, I noticed my lower unit lube is milky. Is this bad? My hope is there is just a little water(?) in it. Will it hurt the motor running it this way? Any help would be greatly appreciated. Thanks. Mike
Mine was like that to, I heard that it is just the water coming in from the top part of the motor. I replaced mine like you should every year. Just to make sure contact a near by dealer
It’s all a matter of degree, but it’s definitely not good. If you decide to leave it, the main thing will be to get that stuff out of there before the first hard freeze – the water will expand and crack the housing. 
It’s too easy to change so let’s not leave it there. The lube doesn’t cost much but the repairs will. I would have to say drain it and refill and I would do it again after a few trips on the water just to check it out. You may find it was just a buildup of condensation inside that made it milky, but if it gets milky after a few trips then water is getting in and you may need a new seal somewhere. Steve
One way to find out if you have a bad seal is to let the motor hang down and if possible, slightly inward. Lay a newspaper or shop towel on the ground below the lower unit. After a day or so check for oil on the paper. If there is any you have a bad seal. If not, and the lower unit isn’t cracked, I wouldn’t worry about it. If no water came out when you pulled the plug, again, I wouldn’t worry. Seldom will you ever find new looking lube after running the motor and pulling the plug.
I had a problem with milky lube, but all I needed to do was get a new gasket for the drain screw. You may also want to remove your prop to see if there is any mono/line wrapped around the shaft since that may be letting water in???? I’ve heard you need a good seal with the prop washer…
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