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Water in gear oil?

Seaworthy1

New member
Is this water in my gear oil? Volvo DuoProp outdrive. I replaced the oil with Volvo Penta OEM gear oil at the end of last season. The oil came out looking like this after being wet slipped this season.

Doesn't water settle to the bottom? Does Volvo gear oil change from honey yellow to dark black as it is used? Is the green coloring water intrusion? This oil has been sitting for about a week so I was expecting to see water at the bottom, but I've read that the gear oils are formulated to keep up to 10% of water suspended. Is this so?

Volvo gear oil is honey colored and very light. Mercruiser oil has a green color to it when new that darkens as it gets used. I was thinking maybe the previous owner was using Mercruiser oil so this is some of the mixed residual oils as the drive was used and the gears spun, but I recall last year the oil came out rather dark.

The drain plug o-ring is extremely small on this drive and it typically gets pretty beat up after it is installed, so could it have come in from there? Last season the o-ring came out looking the same though. It was the proper volvo penta o-ring as well. All 3 o-rings get changed each season with Volvo Penta OEM proper o-rings.

What am I dealing with here? Is this definitely water intrusion? Should the water be settling to the bottom after being in a container like this for a week or two? The container I poured the oil into had a little residual antifreeze in it so that may be floating up top as well, but it minimal.

Debating if I should pull the drive and pressure test it.


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Is this water in my gear oil?
I would say yes!

Volvo DuoProp outdrive. I replaced the oil with Volvo Penta OEM gear oil at the end of last season. The oil came out looking like this after being wet slipped this season.

Doesn't water settle to the bottom?
If stagnant.... yes.
If the oil became hydrogenated... no, it will remain mixed for quite a while.


Does Volvo gear oil change from honey yellow to dark black as it is used?
Only when it becomes contaminated.

Is the green coloring water intrusion?
Water generally turns the oil into a milky color.

This oil has been sitting for about a week so I was expecting to see water at the bottom, but I've read that the gear oils are formulated to keep up to 10% of water suspended. Is this so?
That is considered to be hydrogenated oil.

Volvo gear oil is honey colored and very light. Mercruiser oil has a green color to it when new that darkens as it gets used. I was thinking maybe the previous owner was using Mercruiser oil so this is some of the mixed residual oils as the drive was used and the gears spun, but I recall last year the oil came out rather dark.
I think that some Merc gear lubes are greenish.

The drain plug o-ring is extremely small on this drive and it typically gets pretty beat up after it is installed, so could it have come in from there?
O-rings are not intended to be re-used.

Last season the o-ring came out looking the same though. It was the proper volvo penta o-ring as well. All 3 o-rings get changed each season with Volvo Penta OEM proper o-rings.

What am I dealing with here? Is this definitely water intrusion? Should the water be settling to the bottom after being in a container like this for a week or two?
Not always.
Consider yourself lucky that it did remain hydrogenated.
When it becomes separated, that is when rust will/can occur.


The container I poured the oil into had a little residual antifreeze in it so that may be floating up top as well, but it minimal.

Debating if I should pull the drive and pressure test it.
You can perform a Pressure/Vacuum leak down test with the drive installed.
The oil must be drained prior. The vacuum test doesn't care, but the pressure test does!

The goal is to have it hold both pressure and vacuum for a duration.... hence the "leak-down"!

For best results, bump the starter motor (that will turn the main drive gear), operate the shift mechanism (that will spin the eccentric piston) and spin the prop shafts while the drive is under pressure and vacuum.


While this test may not point to the leak's location, it will indicate if a seal or two are leaking.
If so, replace all.




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