Mercury 15Hp foamy oil discharge

LT Jones

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Apr 16, 2010
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10
Hi,
I have just purchased a 2001 mercury 15Hp in very good condition (so I thought) and may be it's OK. But on my first outing everything appears to be OK apart from this discharge see image. Can anyone tell me if I'm worring about nothing. It is dry now in the photo but it looks like frothy Coffee.

Thx
 

Dave1027

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May 25, 2010
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Re: Mercury 15Hp foamy oil discharge

LT, you should drain the lower unit oil and check it so you know what you have there. Relic is probably correct but regardless, any time you buy a used motor you should check the condition of the seals.
 

LT Jones

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Apr 16, 2010
Messages
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Re: Mercury 15Hp foamy oil discharge

Thanks,

I plan on checking the lower oil anyhow as it's new to me I was also going to change the impellar as preventative maintenance. So the color of the oil should be telling.
As regards the amount of discharge I don't get that much at the moment not as much as Relic but it is the same color and it's bubbley as if it comes out that small hole under pressure. It most have come out of the larger hole to as when it dries out it creates the stain you see in the picture.

Should there be one or two holes in that casting?
The small pin hole does not look right as if it's a poorous casting. Or decay as in a tooth.

Is there any seals that may need to be look at in that area under the powerhead?

I have enlarged the original image to make it a little clearer.

Thx for your help
 

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joed

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Re: Mercury 15Hp foamy oil discharge

Does it also come out of the prop? If it does then it could just be unburnt oil from the fuel mix.
Are you sure that one is a pin hole or is it plugged. I seem to remember my 9.9 (very similar to your 15) had two holes there.
 

LT Jones

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Apr 16, 2010
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Re: Mercury 15Hp foamy oil discharge

Joed,

OK a took another look at the smaller hole and it was plugged. I looked at the prop and it's clean no oily residue Black or Coffee colored. The smaller hole and the larger hole seem to be the exit of two different passages in the casting. I think that after running yesterday and with the moisture it soften and became unplugged. Both holes look as if it was there all along. When I used a dentist's tool to reach up into the cavity there is more of the residue of oil and water but not much. So I think I'm OK. May the smaller hole should larger so it does not plug.

But now I wonder what is the purpose of the two holes are.

Where would the water be coming from?

I will be dropping the oil tonight to check

I also came across this thread

http://forums.iboats.com/showthread.php?t=241608

Thx
 

LT Jones

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Joined
Apr 16, 2010
Messages
10
Re: Mercury 15Hp foamy oil discharge

Can anyone tell me what's the purpose of the two holes?

Thx
 

joed

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Sep 28, 2002
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1,132
Re: Mercury 15Hp foamy oil discharge

On my 1995 they are part of the exhaust system. The oil could be unburnt oil from the fuel mix.
 
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