Lower Unit on a 96 Mariner 150 Magnum leaking gear oil

Metatron

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Aug 6, 2008
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Hey gang! I've owned a boat for about 7 years now so I'm gradually learning more with each passing year. I'm a little puzzled by this problem and before I tear into the lower unit I thought I'd seek out some direction.

Weeks ago I took it upon myself to change the water pump. That seemed to go just fine. I replaced the impeller, but didn't go after the seals under the housing.

I took to the lake and spent a few hours out there running it and fishing. I pulled the boat out and parked it at home, everything looked good. The next morning is when I noticed some clear gear oil leaking out of a hole (not sure what to call it but it's called out in the picture). I just dumped a fair amount of money into the motor for an unrelated issue so seeing that put me off and I couldn't stomach investigating at the time.

I did some reading on the forums and learned that my problem could be seals near the shift shaft but I'm wondering if it has anything to do with not replacing the seals under the water pump housing.

I know the only way to be sure is to look so tonight I plan on pulling the drain plug to check for water but in the mean time I'm wondering what you think Could there be a seal breakdown near the shift shaft? Are leaks in this location typical when a particular seal or ring fails? I'd like to handle this one on my own and avoid the substantial hit to my wallet if I can. Thanks for the help!

MM
 

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CharlieB

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Joined
Apr 10, 2007
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The verticle shaft seals are not normally changed during water pump service.

The LU is tested with only a few psi pressure and also tested with a few inches of vacuum, it must pass both tests or resealing is recommended.

A Factory Service Manual is always a very wise investment, it clearly details the break down and reassembly of the LU changing seals. Not that difficult if you are decently handy with things mechanical.
 

Metatron

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Joined
Aug 6, 2008
Messages
4
I figured it out! I pressurized the lower unit and could hear a leak. Took it apart and turns out I had a leak at the water pump base. Replaced the base and I'm in business.
 
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