Gear Oil Color?

**Good Stuff** · 12-02-2012, 06:37 PM

I use Evinrude Synthetic lower unit gear oil in my motor. When I put it in it is clear but when I drain it it is milky looking. So the logicall thing to think is water is getting in ,right?
I pulled the lower unit and did a complete seal job and put back together. I ran the boat this weekend and pulled the plug today to test the color and guess what? Yep it has the same milky color

. So I decide to do a pressure test to find where the leak is and was going to use my clear hose that use to fill the lower unit with new oil. It had some oil in it from where I last used it. I put my mouth to it to blow out the oil so that I only have air going in the lower unit and when I did the clear oil that was in it turned milky white

.
So my question is can the oil maybe just turning milky fron the air in the lower unit mixing with the oil when the gears turn and not water intrusion?
By the way I went through with the pressur test and it held 15lbs. for 30 min.

**Archerguy1** · 12-02-2012, 08:08 PM

A lower unit has about an inch of air space above the level screw to allow fo expansion when running and the oil gets hot, many drive shafts have a spiral cut in them so as they turn it slings oil up to the top driveshaft bearing, thus forcing the air in the top down into the oil airating the oil. The only true test for water intrusion is , after running the motor on the lake , tilt it down and let it sit for a couple of days, any water will go to the bottom and be visable when you crack the bottom screw loose (like an oil spill water is heavier than oil) and the time allows all the air to work it's way out and back to the top. Johnson / Evinrude motors should hold 15 psi on a presure gauge for at least 20-30 mins and Merc/Mariners won't hold over 7-8 psi before you blow the shift rod bushing seal out

**Good Stuff** · 12-02-2012, 08:27 PM

I have checked the oil after fishing and it sitting for a while like you say and no water comes out so I am going to assume the milky oil is just air mixed with the oil.
By the way, my motor is a Mercury 135 and it will hold 15lbs.

**skeetbum** · 12-03-2012, 08:03 PM

Good stuff, listen to the man. He knows of what he speaks.

**jigflinger** · 12-03-2012, 08:37 PM

Good information, Archerguy1. Thanks for posting.

**Archerguy1** · 12-03-2012, 09:04 PM

Originally Posted by Good Stuff

I have checked the oil after fishing and it sitting for a while like you say and no water comes out so I am going to assume the milky oil is just air mixed with the oil.
By the way, my motor is a Mercury 135 and it will hold 15lbs.

I have seen the Mercs and Mariners loose presure above 7-8 lbs because if you look at the lower unit or look for a blow up pic of the gear case you will see the shift rod seal in the shift rod bushing has nothing to hold it down , now over time there may be some corrosion built up on the aluminum bushing and a steel lip seal that holds it in place under higher presure, but for the most part a newly re-sealed gearcase with pop that seal out of a bushing around 7 psi

**Good Stuff** · 12-03-2012, 09:20 PM

Isn't the shift shaft rod seal built into the nut that screws down?

**Turtlebait** · 12-04-2012, 06:10 PM

Try reg. grear oil,sound like the syn. Is foaming.

**Good Stuff** · 12-04-2012, 07:21 PM

Originally Posted by Turtlebait

Try reg. grear oil,sound like the syn. Is foaming.

I'll have to look into this more

**Archerguy1** · 12-04-2012, 08:20 PM

Originally Posted by Good Stuff

Isn't the shift shaft rod seal built into the nut that screws down?

Shift rod bushing screws into the gear case with the tab tool, shift rod seal presses into the bushing from the top down into the bushing and when it's together and installed nothing holds the seal down , high presure can push the seal out from the bottom

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