# Help: Lower Unit Leak?



## airdawg11 (May 10, 2012)

I just bought a boat and I noticed a little oil on the floor. Looks like lower unit oil from around the prop. It is an older Mercury 9.8 hp Model 110. Anybody have any experience with this, and what to do. Im sure there is a seal around the prop, but I have no idea how to get to it or change it. I really dont want to spend 150 or so to fix it at a mechanic, when its probably only worth 300-400. Any help is appreciated!


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## nomowork (May 10, 2012)

Are you sure it's not oil from the exhaust?

The best advice comes from the outboard's manual. Worth the few bucks to get one as many motors have different seal configurations. From experience, I don't trust whoever worked on it before I did as I have run across seals that were installed backwards, missing seals, etc.


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## airdawg11 (May 10, 2012)

No im not sure its not oil from the exhaust, I did just start it up for the first time since last year (per the guy I bought it from). So a little oil may come out of the exhaust after sitting for awhile?


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## Johny25 (May 11, 2012)

Isn't this the same post I am responding to????? Or am I having Dejavu?


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## nomowork (May 11, 2012)

I keep a small metal pan under the prop when I park my two stroke boat, especially after an outing as two stroke exhaust oil will drip for a short while.

If you're sure it's lower unit oil, I'd look into it as that might be a sign or worst things to come.

Is this Bizaro world? :roll:


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## airdawg11 (May 11, 2012)

Ya johny this is the same post, Im new to the site and didnt realize there was a motor forum, until I posted this. I took the boat out for the first time today and their is milky looking oil coming from around the prop. The motor ran fine and didnt seem to have any issues. So hopefully the lower unit is not damaged and I can figure out how to fix the leak and change the lower unit oil. Anybody have any experience on how to fix it? I imagine there is a seal behind the prop, just dont know if it can be changed without special tools.


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## Johny25 (May 11, 2012)

If your lower unit does not have water in it and it is still full of gear oil then it is not the seals. My guess is that it is unburnt fuel still and your motor may be running a little to rich possibly


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## airdawg11 (May 11, 2012)

Im going to have to drain the lower unit oil to see if there is water in there. It was a decent amount of ail coming from behind the prop, not out of it. I sure hope its just me mixing my oil too rich, but Im afraid it is out of the lower unit. I may be able to post a pic of the oil, i put down some cardboard under the engine to see how much is leaking and to keep it off the garage floor.


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## airdawg11 (May 11, 2012)

Okay scratch that last comment from me. After looking over the motor more closely there is some grey oil coming from the exhaust port on the prop and it smells kinda gassy, but it mostly is coming from behind the prop. I guess I should still drain my lower unit oil. But I guess I should try to mix my oil a little leaner. I used 50:1 today, but maybe ill try a little less oil. Johnny if I am mixing it too rich, will a decent amount of unburnt oil come out? Probably 1-2 oz. or so came out I guess...


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## airdawg11 (May 11, 2012)

Johny looks like your probably the man. I found this post on google...

78 Merc 1400 outboard grey sludge out the exhaust?

Hi All,

I was working on my boat in the driveway and was running the engine and noticed that when I shut it off I had a lot of grey sludge/foam coming out from the exhaust thru the prop.

I thought it was the oil/water seals leaking from the bearing carrier. So I replaced both the front seals and the rear o-ring. Replaced everything and filled the lower unit with oil.

I ran it again and it still has the grey sludge/foam coming out.

Now is this because it is sitting in the driveway idling and the grey sludge/foam is just unburnt fuel and oil?

TIA for the help	2002-06-29
corm	Hi,
Yes, all it is is unburnt oil and water mix.
It is normal in smaller amts. If you have great gobs of it you may have to rich of mix or a miss
causeing excess fuel to be discharged down the exh
tube.


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## Johny25 (May 11, 2012)

Stick with the 50:1 mix and do not run leaner fuel. Try adjusting your carburetor instead. I don't know mercs well so I wouldn't know how to tell you to do it on a merc. You may have a slow speed idle screw that will lean out the motor.

Some years ago I changed the seals in my 9.9 johnson thinking the same thing you were thinking, only to find out the seals were fine and I still had some exhaust leakage  Basically the same thing that guy did that posted that on google :lol: 

1-2 oz is not excessive and you should be fine


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## oukast (May 12, 2012)

My lower unit leaks a little too....not just from exhaust residue either. (I run 100:1 Amsoil) Some smart guy had a leaking seal on the lower unit and put a big gouge in the seal housing getting the old seal out. Now it leaks worse with the new seals than with the old....I keep i topped off with quality gear oil and at the first sign of water intrusion I drain and refill completely. One of these days that smart guy will take it back apart and use a quality sealant along with new seals, but alas he is to cheap to pay the $30 BRP wants for the seals. Moral of my story is keep an eye on it and if it is seals make sure you don't gouge the housing when you replace them or you will be worse for the wear.


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## Johny25 (May 12, 2012)

flirting with disaster at 100:1 [-X OMC corrected the recommended 100:1 to 50:1 on there motors after engines started blowing up. My advice would be to not let that smart guy mix your fuel anymore either :lol:


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