Massive Gear case oil leak

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Asaracing21

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Sep 6, 2013
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1996 Mercury 2 stroke 9.9, Started the engine and it would run only on choke and if i played with the gas but it did always idle better than when I did give it gas. Well after I played with it enough I was able to start to clear the engine out (neutral gear) Slowly I noticed my water becoming more and more gray. Eventually the entire bucket I was using had all 6.8 ounces of gear case oil floating and on the sides. After talking about it with the old man the engine probably was choking it self with water since the oil was also coming out of the very top mid section suffocating the exhaust. This would explain why it ran decent at a low idle and then when I tried to clear it out the pump forced water up through the mid section causing it to suffocate. Now we think the guide to the water pump and water tube up through the mid section is a very sloppy fit and we think this is the culprit but I want to ask others what they think. I did replace this water pump and all the seals....
 
MH Hawker

MH Hawker

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Re: Massive Gear case oil leak

mmm it is common to have un burnt 2 stroke oil in a tub when test running, and being as you were choking it, its even more. Now if you losing LU oil it will also have water in the LU. As far as the water pump seals, the top of the tube has a rubble sleeve type that is very hard to fit in a socket in the bottom of the power head and some one in the past may of not got it in place. You will have to pull it apart and see.
 
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Asaracing21

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Re: Massive Gear case oil leak

MH Hawker said:
mmm it is common to have un burnt 2 stroke oil in a tub when test running, and being as you were choking it, its even more. Now if you losing LU oil it will also have water in the LU. As far as the water pump seals, the top of the tube has a rubble sleeve type that is very hard to fit in a socket in the bottom of the power head and some one in the past may of not got it in place. You will have to pull it apart and see.
Click to expand...

I pulled the lower unit there is water in it and drained the remaining not even 1 oz of gear oil. At this point I might as well replace the prop seals. Not sure where to get the seals. Engine serial number is 0g40173. 1996 mercury 9.9 2 stroke
 
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carholme

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Re: Massive Gear case oil leak

You seem to be missing one number from your s/n but it is a '96 and here is the parts list:

6/8/SAILMATE 9.9/SAILPOWER 15 H.P. - Mercury, Mercruiser, Force, etc. Parts Lookup

The first thing to check would be items 4 and 9 under GEAR HOUSING (DRIVE SHAFT)(2.00:1 GEAR RATIO) as they are notorious for leaking. For the amount of oil you leaked and water taken in, one may even be missing. Was any work done to the LU?

If you would like a copy of the service manual for your engine, send me a PM with an email address and I will forward it to you.

Gerry
 
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Asaracing21

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Sep 6, 2013
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Re: Massive Gear case oil leak

carholme said:
You seem to be missing one number from your s/n but it is a '96 and here is the parts list:

6/8/SAILMATE 9.9/SAILPOWER 15 H.P. - Mercury, Mercruiser, Force, etc. Parts Lookup

The first thing to check would be items 4 and 9 under GEAR HOUSING (DRIVE SHAFT)(2.00:1 GEAR RATIO) as they are notorious for leaking. For the amount of oil you leaked and water taken in, one may even be missing. Was any work done to the LU?

If you would like a copy of the service manual for your engine, send me a PM with an email address and I will forward it to you.

Gerry
Click to expand...

I bought from a buddy which hasn't used it in 2 years it sat in a shed outside. I would assume the temperature changes got to the seals. I live in wi so -10 to 105 degrees .
 
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Asaracing21

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Re: Massive Gear case oil leak

Asaracing21 said:
I bought from a buddy which hasn't used it in 2 years it sat in a shed outside. I would assume the temperature changes got to the seals. I live in wi so -10 to 105 degrees .
Click to expand...

Also yes I put a new water pump on the lower unit a few weeks ago ran it but never leaked. I'm assuming after I ran it the seals let go when I put it away for a bit.
 
MH Hawker

MH Hawker

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Re: Massive Gear case oil leak

Of course I would recommend a full set of seals replacements and then a vacuum / pressure test.
 
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carholme

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Asaracing21

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Re: Massive Gear case oil leak

Yes I looked at the parts diagram, do I just order the parts labled seals? Yes the seals I bought brand new after changing the gear lube. I did see a kit that was on that diagram, had the water pump base and some seals for the prop shaft. This is my first boat and I'm learning as I go I appreciate everyones help
 
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