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9.9 Johnson

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PT1

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I have gear oil in shaft tube. No leaks from what I can tell in lower unit. Pressure tested at 10psi . Why would I have gear oil running down the tube? Motor is a 1987
 
Lower unit should be pressure tested when fully drained. 10 psi may not show a leak with gear oil in place. I drain and sometimes even let the lower unit heat up in the sun. Then pressure to 15 psi and find the leak with soapy water. If GEAR OIL is in the driveshaft tube, (not to be confused with uncombusted oil/gas mixture), it must be coming out the shift rod O-ring or the seal and/or gasket under the water pump. What horsepower?
 
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PT1 said:
I have gear oil in shaft tube. No leaks from what I can tell in lower unit. Pressure tested at 10psi . Why would I have gear oil running down the tube? Motor is a 1987
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I have no idea what that means... however, if what you see running down the skeg via whatever route is more black than anything, that would be the non-burnt mixture flowing down the soot covered interior portion of the exhaust tube. A most common happening on the 9.9hp & 15hp models since 1974.

Compare what you see with the actual gear-lube viscosity and coloring to hopefully ease your mind.
 
timguy said:
Lower unit should be pressure tested when fully drained. 10 psi may not show a leak with gear oil in place. I drain and sometimes even let the lower unit heat up in the sun. Then pressure to 15 psi and find the leak with soapy water. If GEAR OIL is in the driveshaft tube, (not to be confused with uncombusted oil/gas mixture), it must be coming out the shift rod O-ring or the seal and/or gasket under the water pump. What horsepower?
Click to expand...


I have tested at 10 psi with oil drained. Put it in a tank of water and checked for bubbles, none.My gear oil I'm using has a green tint to it so it is very distinct. I just want to be clear , I should have no gear oil in shaft tube . Gear box is supposed to be sealed, correct? I'll increase test to 15psi and see what happens. Thanks for your input . Motor is a 1987 9.9 Johnson.
 
No, not skeg. When I pulled lower unit off yesterday I saw gear oil running down the shaft / leg where drive shaft goes up to motor. My gear oil has a green tint to it so it is very distinct.
 
Is there gear oil in the water pump then? If so its gotta be the upper shaft seal, right? It is more difficult to check this leak with soapy water because the seal is underneath everything. In a bucket of water it may be hard to determine the exact leak site, besides that, the leak may be aggravated by the operation/rotation of the shaft, which may be impossible to duplicate while in the bucket. Could the shaft be bent?
 
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