Milky gearcase lube

Capt Fernando Martinez · Jan 30, 2012

KJH said:
When picking up my 1983 Evinrude 7.5 outboard from maintainance, the marine tech noted that the gearcase lube was "milky". He did note that seals held both pressure and vacuum and seem to be okay.

Not having had a lot of previous experience with outboard engines, as we sail(and therefore,motor) on Lake Michigan, I took this as an indicator that the engine might finally be getting to the point of needing replacement.

Does anyone have any advice they could share regarding this situation? How concerned should I be? As always, I value the many knowledgeable voices of experience.

Ken

Typically when the oil is milky it means that water has emulsified with the oil, which means that at some point water has gotten into the gear case. I suggest changing out the oil if it hasn't been done already. After running some time on the new oil, remove the bottom oil plug and see if water comes out. If water does not come out this is a good sign that the seals are good but it leaves doubt to how the oil got milky. If water comes out then the seals are bad and they need replacement. I hope this helps.

Chris Patterson · Jan 31, 2012

I gotta agree 100% with Mr. Martinez. And with me, it would be a matter of economics. I wouldn't replace a motor for that little transgression. Just me, but I'd change it, and run that thing.
Just keep your eye on it.

watercolors II · Jan 31, 2012

Change oil every fall!

If I do a lot of motoring during the sailing season, I notice some water infiltration into the lower unit, it all depends on how much I use it. I noticed this 20 years ago when I purchased the boat and motor.

The very first winterization project I perform is replacing this gear oil regardless of its condition. Living in a cold winter climate the worst thing to have is water in the oil to freeze and break something.

ShotgunSlim · Feb 1, 2012

I've noticed that gear oil will remain milky looking for a number of hours after running the motor. I came off the river and checked my gearcase lube level and thought I had water intrusion. Letting the motor sit up overnight and checking it the next day, the oil was fine. Apparently, air gets mixed up with the oil during normal operation and will make it look milky until the air dissipates.

shipwreck66 · Feb 4, 2012

After replacing the gearcase seal, O-rings and gearcase oil (numerous times) on my 1964 Evinrude 9.5 I would still notice a milking look after running it. After consulting with a very old outboard shop guy about it he just shook his head and pointed his finger at me and said "I bet you buy that cheap crap from Academy don't you?". Well , yes, I did, the standard Pennzoil gearcase oil. He handed me a couple tubes of really black gearcase lube and told me to fill the case with this, cost about $10 a tube, but haven't had a problem since. He said the good stuff won't allow water to intrude and the cheap stuff heats up and changes chemically, actually drawing water in. So, 1964 model still running just fine.

Chris Patterson · Feb 4, 2012

Hey Shipwreck, what is the specifics, (brand, etc.), on that thick black stuff?
I'm always interested in superior lubricants.

shipwreck66 · Feb 5, 2012

Chris, it's Mercury Premium Gear Lube. Comes in a 8 oz tube that you just squeeze till it comes out the top hole in the gearcase. Just the right amount in the tube to fill up the gearcase of outboards 15hp and smaller.