Milky Oil

After 16 years of owning my own boats I finally have found the dreaded milky oil in my lower unit. The big question is, am I doomed for big $$$ repairs?

I don’t believe the drain and vent plugs were leaking. Both were well tightened and the seals were present and looked good. If that’s the case, where else can it be coming from?

I understand that the shaft seal is one other place. Is a shaft seal relatively easy to replace? Is there anywhere else?

the logical side of me says that the lower unit is fine as far as lubrication but I should not let it freeze with water in it.

Thoughts?

Thanks in advance.

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Yep don’t let it freeze. How long since it was serviced? Likely just a seal, go ahead and get it fixed. That of course is assuming you haven’t hit anything and bent the shaft.

Didn’t hit anything, I’m sure of it. You’re talking about a shaft seal, correct? Not a plug seal…

I changed the oil last September. I usually change it twice a year. I figure I average well over 500 miles per year on the motor. Heck, I put at least 30 miles on just Saturday on mille lacs.

Side note, I also found a small amount of metal stuck to the vent plug magnet. Nothing stuck to the drain plug magnet.

It’s a 2002 Johnson 150.

The shaft seals are not hard to replace. Which one is leaking is the tough thing to determine though. There is one behind the prop and another on the driveshaft below the water pump impeller. Either do both or pick one and monitor the oil to see if you got are still getting water in the oil.

I was thinking of replacing the impeller again so I may as well consider doing the top one when I do that.

If I recall they sell whole seal kits. Yours original? If one is starting to go might as well do them all with all the miles you put on.

Have you noticed any slippage in your gears? See alot of guys try to feather into forward and reverse where it’s quite the opposite, sure ya know just a PSA.

I got my reverse dog going, but figure can nurse that out for a year or two still hopefully.

Are you planning to replace the seals yourself? If you do pressure test the unit before you fill it with oil to make sure it won’t leak.

By slippage, do you mean it chatters when putting it in gear?

Mine engages in one nice clunk. Both forward and reverse.

onestout wrote:

Are you planning to replace the seals yourself? If you do pressure test the unit before you fill it with oil to make sure it won’t leak.

I’m sure I can do that. I’d assume you’d bubble test the seals and plugs?

just be sure to use low pressure when testing,no more than seven pounds psi.
a vacuum test is a better way to test the water side seals,three inches of vacuum is plenty.
both tests should be able to hold for a few minutes if everything is right.

dont forget,some units use o-rings as well to seal housings like the water pump housing on its outside diameter,the lower unit bearing carrier uses an 0-ring on its outer diameter as well.

check for loose bearings while you are at it.
on my own outboards,I use a half and half mix of lower unit oil and lucas heavy duty oil stabilizer as I want all of the protection I can get,those lower units dont have the easiest life in the world.

Update.

Replaced lower drive shaft seals. Ran probably 30 miles on Mille Lacs. Opened the drain plug for a looksee. Oil looks much better. Slight milky appearance but that due to slight residual oil from before the seal replacement.

I put a slight gash in the lower unit housing sealing journal while removing the seals. It didn’t appear to go all the way across the seal surface so I hope I’ll be ok.

Problem solved in my book.

Thanks guys.

I have a 70 hp that I check every fall for milky gear oil. I do not change but every 5 years. Changing every year without leakage evident is a waste of money. Lower units do not see anywhere near the use that a truck differential does and you certainly would not change that every year. My brother bought a new 90 Etec went 5 years without checking. Checked in fall, it was completely dry. He filled it and ran with no problems 4 years since. Feels strongly dealer never put any in lower unit to start with as he has noted no leaks since he filled it. Certainly reinforced my point.

I think my manual calls for the lower unit to be checked at 15 psi, but i would have to look to be sure. I just pump it up and make sure it doesnt leak down.

Good to hear all is fixed. Went through that in my duck boat last year, it’s no fun.

I gouged the sealing surface on my ATV’s rear diff cover yesterday replacing the axle seals. It didn’t leak when I took it for a test run, but I’ll just keep an eye on it. I also took a pick to the hand when tugging on a seal…that gets your attention quick!