Mercury 9.9 lower unit vent hole leakage

CaptTorS

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Joined
May 28, 2013
Messages
23
I bought new seals/washers for both drain& vent holes, when I seem a little oil running down out of vent hole after boating. Put in some more oil til it came out top, using a pump, and put new bolts & washers on, tight. Came back a minute later & oil is running down side again. Anyone know what's wrong? Too much oil? Thanks
 

Mi duckdown

Commander
Joined
Apr 14, 2007
Messages
2,575
Re: Mercury 9.9 lower unit vent hole leakage

make sure there is not any of the old seal/washer stuck on lowerend case. use a small screwdriver or pick and scape it.
 

CaptTorS

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Joined
May 28, 2013
Messages
23
Re: Mercury 9.9 lower unit vent hole leakage

make sure there is not any of the old seal/washer stuck on lowerend case. use a small screwdriver or pick and scape it.

Yes, I made sure, I scraped it out and made sure there was a good clean seat for the washer. How can oil suddenly appear after that? Is there pressure build up when not running?
 

CaptTorS

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May 28, 2013
Messages
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Re: Mercury 9.9 lower unit vent hole leakage

I was going to post an update to the situation, but I see that would be pointless
 

snowman48047

Petty Officer 1st Class
Joined
Jul 24, 2008
Messages
371
Re: Mercury 9.9 lower unit vent hole leakage

Not much that can be wrong other than what was posted, a bolt in a hole with a seal. I had one the threads were stripped, so it leaked. What did you find?
 

CaptTorS

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May 28, 2013
Messages
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Re: Mercury 9.9 lower unit vent hole leakage

Not much that can be wrong other than what was posted, a bolt in a hole with a seal. I had one the threads were stripped, so it leaked. What did you find?

I haven't found why for sure yet, but I did tighten far tighter than what I felt was necessary or safe, and it did not leak. I really don't think it should have to be that tight.
 

gonogo

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Joined
Mar 30, 2008
Messages
14
Re: Mercury 9.9 lower unit vent hole leakage

Need to be very tight on new gaskets, they are hard, not soft. On my 9.9 I changed oil once and bought new gaskets, the old looked good so I used them over, no leaks.
 
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