Logo
FULL SITE MENU

Duo prop gear oil turned black

K

kingsfisherman

Regular Contributor
Hello All,

The other day I removed my drive and found the pinion seal was leaking so i began the repair process.
When I drained the gear oil it was very black and smelly. It has been awhile since I changed the oil because when ever I checked it it looked clear on the dipstick. I also recently added some gear oil (Pumped in from the drain plug of coarse.)
Any ideas on what happened?

TIA
 
what I find interesting is whenever I checked it looked clear so I thought all was well. It has been sitting since May so maybe it happened on the last trip.
 
kingsfisherman said:
what I find interesting is whenever I checked it looked clear so I thought all was well. It has been sitting since May so maybe it happened on the last trip.
Click to expand...

Many gear oils will become hydrogenated with small amounts of water intrusion. When the oil remains hydrogenated, it will typically not cause any rust damage.
However.......... if given enough time, the water may eventually separate from the oil, allowing gravity to pull it to the lower areas, of which may explain why you saw clear gear oil at the upper area. Meanwhile, carbon steel rust is developing at the lower area.

If you see signs of rust (such as the dark colored gear oil), it may be time to pull the drive apart and examine all of the components.
Typically the precision bearing surfaces will be hit the hardest and may cause the most damage.


.
 
Well i'm still getting some water into the drive, I drained the oil and its milky again after only a few hours of use. Also noticed the u-joint assembly was rusty and bellows had water intrusion. I'm going to pressure/ vacuum test the drive but not sure whats going on with the bellows letting water in, did it according to manual and still seeing sighs of some water.
 
......................
kingsfisherman said:
Hello All,

The other day I removed my drive and found the pinion seal was leaking so i began the repair process.
Please explain what you are calling a "pinion" seal.

Your drive will have a transmission (upper gear unit) "drive" and a "driven" gear, and the lower unit will have one "drive" and two "driven" gears.


When I drained the gear oil it was very black and smelly. It has been awhile since I changed the oil because when ever I checked it it looked clear on the dipstick.
If you will check the dip stick shortly after the engine/drive have been operated, any contaminants will become more visible.


I also recently added some gear oil (Pumped in from the drain plug of coarse.)
Any ideas on what happened?
If the gear oil is turning dark, it is likely a result of water intrusion that has caused iron oxidation.
See post # 6 again.



I would suggest that you drain the gear oil and perform a proper Pressure/Vacuum leak-down test..... Key words "leak-down".


TIA
Click to expand...
 
Last edited:
Back
Top