Dp-sm outdrive... why won't my oil drain?

mklearl

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1998 dp-sm 1.95:1 outdrive. I'm not too familiar with outdrives but I guess I'm going to learn just like I did with the motor. Long story short the boat sat for over 10 years. On the outdrive I changed the oil at the beginning of the season. It flowed out slow. Yes... I removed the drain bolt, vent screw and dip stick. After about an hour draining it went from slow to barely a trickle. I figured close enough since the oil coming out was clean albeit 10 years old. When adding oil I had my 3 quarts of 75w90 and was prepared to pump in 81 ounces from the bottom up. About half way through my 2nd quart it starts coming out the vent hole, indicating it's full. I thought maybe I had an air pocket in there. Spun the props and the yoke. Tried to pump more in but it just came out. I figured it was full and called it good.
Fast forward to now. Used the boat for about 70 hours this season. Checked the outdrive oil throughout the season. The level maintained right on the mark all year. It got a little darker but not black... it was still translucent. I go to winterize it and pull the dipstick and the oil level and color are as described above. Unscrew the vent and drain bolt and the dreaded milky oil starts to ooze out. Not white but a gray. So now I'm worried because of water intrusion. It still oozed out like lava or molasses. I waited about 3 hours to let as much drain out as possible. I was strapped for time and couldn't perform a pressure and vacuum test on it (I know... I should have done that at the beginning of the season... be gentle!) But I was nervous about the water in there so I didn't want it to sit without any lube in there just rotting until i could get to it. So I started pumping my $20/quart gear lube in. About half way through my 2nd quart, gear lube starts coming out the vent hole. It looked a bit dirty so I kept pumping the rest of that 2nd quart until it came out clean.
So now I need to do a pressure test to find out where the leak is. But I need to drain the oil to do so. Why am I not able to drain all the oil? Thanks in advance!
 

Fishhead-1

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Oct 10, 2003
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hi, what type of gear lube are you using? Are you using synthetic gear lube without LS additive? With the drain plug removed and dipstick out you could try to blow the remainder of oil out through the dipstick hole with shop air.
 

mklearl

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Volvo penta 75w90 synthetic gear oil. I put my thumb over the vent hole and blew through the dipstick tube. There was no resistance like I thought there would be like if it were plugged or there was lots of oil in there. Just straight out the drain plug... no aditional air. I'm sure compressed air can force more out than my lungs... but a quart of oil is a lot not to just be flowing out.
 

bruceb58

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Was your drive all the way down when you drained the gear oil?

Do you replace the o-rings on the drain, vent and dipstick when you change your gear oil?
 

Fishhead-1

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Your right though a pressure test and repair and a good flushing after with lube and you'll be fine. A lot of us use the amsoil synthetic gear lube its less than half that price.
 

mklearl

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Was your drive all the way down when you drained the gear oil?

Do you replace the o-rings on the drain, vent and dipstick when you change your gear oil?

Sorry. I didn't mention that. I actually took the drive off last year to change bellows, check alignment, replace water intake components etc. I put new O rings on all three... dipstick, vent, and drain plug.
Drive was in the vertical (down) position for 3 weeks prior to draining. I will say that it was stored up for 10 years prior to me getting my hands on it.
Good to know about the Amsoil. Thanks
 

bruceb58

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I use the Volvo lube. If you buy it in gallon sizes, it's cheaper than buying it by the quart.

You use the filler adapter that screws into where the drain plug goes?

I find that it is easy to damage the o-ring that goes on the drain plug that is behind the prop. I cover the threads with electrical tape and then roll the o-ring over that onto its position.
 

mklearl

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I use the Volvo lube. If you buy it in gallon sizes, it's cheaper than buying it by the quart.

You use the filler adapter that screws into where the drain plug goes?

I find that it is easy to damage the o-ring that goes on the drain plug that is behind the prop. I cover the threads with electrical tape and then roll the o-ring over that onto its position.

I believe I saw you post that somewhere and that is precisely what I did. There is some rust around the propshaft seal and the rubber seal itself looks a bit rough. The pressure test should reveal the culprit. My problem is that I can't get an accurate pressure test unless the drive oil is drained. Why is there at least a quart stuck in there and how do I get it out?
 

Scott Danforth

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I find that it is easy to damage the o-ring that goes on the drain plug that is behind the prop. I cover the threads with electrical tape and then roll the o-ring over that onto its position.

a short section of straw from your local burger joint works as well to cover the threads. Also, if you keep the insertion sleeves from valve seals,that works as well.
 

Scott Danforth

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I personally like the crush washer vs o-rings
 

Fishhead-1

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i think your right the book calls for 81 ounces in a dp-sm but every year servicing mine it only takes a little more than 2 qts. I would think 81 ounces would be overfilled. Maybe someone else knows exact
 

mklearl

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I'm at about a quart and a half. I know draining it completely dry is not possible but a quart still in there concerns me. I'm curious if there are different channels in there and somehow one is blocked.
 

mklearl

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So back at this finally and I'm ready to work on it. I started draining the fresh gear lube out to do a pressure test and grey, milky oil started coming out. Considering I removed the outdrive and it's been sitting in my garage since I changed the oil I'd say that all the oil didn't completely drain out last time as I previously assumed. Anyone have any thoughts on this as why it won't drain? Should I just get it as empty as I can and do the pressure test? Thanks in advance.
 

bajaunderground

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Is there any way to warm up the drive (space heater, salamander heater, etc.)? might help with the flow? I would say using pressurized air at the dipstick would put the wrong kind of stress on the seals...from my understanding the seals are designed to keep water out, not pressure in; however, when my outdrive was pressure tested the shop put 15psi on it for 24 hours. Not sure if adding a little pressure would force the lube out?

Is there an fluid one can use to flush it out? Kerosene, mineral spirits, etc?
 

mklearl

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The oil was changed after running and on a fairly warm day. The oil looks like I never changed it... n?e oil mixed in with about a quart of the stuff left in there. I can plug the vent hole and blow freely down the dipswich hole. There is no restriction. When filling, oil is pumped freely up to th vent hole. There must be different channels that the oil goes through to distribute oil all around the gear case. My guess is that one of these channels is clogged somehow leaving half the oil in there. If I seperate the lower gear housing from the upper, would I have access to thesee channels to find the potential problem?
 

mklearl

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So I let it drain all day and got the usual amount out and did a pressure test and it held 15psi all night. I'm not sure if that's really accurate considering there is still some oil in there.
 

BRICH1260

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Do a vacuum test also. My outdrive oil was milky. It passed a pressure test but failed the vacuum test.
 

mklearl

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So I did a vacuum test. I pumped to 15 inches and left for a couple hours. When I came back I was down to 6 inches. So I grabbed the manual and realized that the test should only be performed for 3 minutes (probably should've read the manual first). So I did it again and it held 15 inches for 3 minutes. I moved the propshaft, shifter, and driveshaft during the 3 minutes. So am I to assume my seals are fine? I'm curious where the water came from then.

I did change one seal which was the one that goes around the water tube... it was pretty beat up and cracked. Could that cause water intrusion to the oil?
 

Grub54891

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Not sure on yours. but most mercruiser I've worked on only require 5 inches of vacuum. Yours may be different than that though.
 
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