Lower unit oil -- water or not?

[woodycooper]

I normally use Mercury or Yamaha lower unit oil which is dyed blue. When I drain it after a season of use it is normally pretty dark and no signs of water. Recently I hit something hard, destroyed a stainless prop. The shaft still looks straight, but I decided to drain the oil anyway. There was maybe a drop of water in the whole thing, nothing to worry about. I refilled it with cheap gear oil with no dye, ran the boat maybe an hour, then drained it. Pictured is a sample which looks milky to me, but others have said it could just be mixed with air from the gearcase. I took a small amount in an aluminum can and heated it up on the stove. It quickly bubbled some and within a minute it was completely clear. Does this indicate a small amount of water? I pressure tested and the gearcase holds 10 PSI or even 20 for a long time, like I let the pressure off after 20 minutes. I did not vacuum test however, but my understanding is that this would be for different temperature of oil and the outside water causing a pressure difference, sucking in the difference in water. I drained and filled again, with the same cheap gear oil and ran for approximately 160 miles, got the same result, good pressure test, looks like milky oil to me, and the same very small amount of metal shavings on the tip of the drain plug. Is this just air bubbles in the oil or is water somehow getting in? TIA, Woody

 

[Chris1956]

Water is present, IMO. Let the mix settle and it might separate.

 

[Scott Danforth]

that is water/oil emulsion

 

[Crosbyman]

could be just emulsified.... has suggested let it settle in a clear jar a few days . water will be at the bottom.

when you refilled did you use new washers and torqued it to specs

 

[woodycooper]

that is water/oil emulsion

I figured. Any idea where it could be coming from? My understanding is that there are only two places, the water pump seal and the shaft seals, right? A water pump servicing is needed anyway, maybe I should just replace 'em all.

 

[airshot]

Possibly the combined two different lubes...I have saw some weird colors come out when two different lubes were mixed together.

 

[racerone]

Air bubbles.-----Let motor sit for a week before checking oil in lower unit.----Check or have shaft checked for run out.----Destroying a stainless prop usually results in a bent propshaft.----A shop would use a dial indicator and not eyeball it.

 

[woodycooper]

Air bubbles.-----Let motor sit for a week before checking oil in lower unit.----Check or have shaft checked for run out.----Destroying a stainless prop usually results in a bent propshaft.----A shop would use a dial indicator and not eyeball it.

Roger, bent shaft affirmative. The oil had sat in the boat for a week, then I idled maybe a 1/4 mile, pulled it onto a trailer. I don't think idling could mix 90wt oil that thoroughly, but I'm treating this as if water was in the oil. I still don't understand why I need to do a compression and vacuum test, but I assume one seal seals out water and the other seals in oil.

 

[Faztbullet]

Air in oil

 

[KJM]

I think its water in your oil. It bubbled when you heated it and then went clear. That was the water boiling off and leaving clear oil, IMO. If you tried that again in a covered container pot you could see if it produced water droplets on the cover from steam being released. But be careful not to start a fire!

 

[Scott Danforth]

I figured. Any idea where it could be coming from?

Pressure test and find out

 

[jimmbo]

I figured. Any idea where it could be coming from? My understanding is that there are only two places, the water pump seal and the shaft seals, right? A water pump servicing is needed anyway, maybe I should just replace 'em all.

Don't forget the Seals for the Fill/Vent/Level Screws

 

[saltchuckmatt]

Put some blue stuff back in. I used some lubermatic stuff once with similar colors. After draining it, the dealer and I determined that it wasn't water and the oil itself had separated.

Not sure if that is what happened to you but trying your blue stuff would confirm either way.

What brand did you use?

 

[woodycooper]

Put some blue stuff back in. I used some lubermatic stuff once with similar colors. After draining it, the dealer and I determined that it wasn't water and the oil itself had separated.

Not sure if that is what happened to you but trying your blue stuff would confirm either way.

What brand did you use?

I already pulled the bearing carrier and have replaced the seals just to be sure. Yes I'm going back to the expensive blue stuff when I fill up. It's better oil anyway and I'm used to the way it looks when used. I had used just 80w90 gear oil until I could determine if and where it was leaking so as not to waste a whole bunch of expensive oil. I drained it several times attempting to determine if water was in it or not.

 

[woodycooper]

Pressure test and find out

I think I said in my OP that I had pressure tested good, but not vacuum tested. That's why the confusion -- shouldn't be water according to the test but yet it appears there is.