Fill the Outdrive from the middle or bottom?

Jake707

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ok i have another thread going for a different issue on my 89 bayliner with a 2.3 OMC combo but i wanted to get some clarity on how to fill the outdrive. I check the oil level in the drive way and its just to the bottom of the dipstick so since i just bought the boat i might as well change the oil for peace of mind. I bought 2 quarts of Sierra Premium gear oil that says its for use on outdrives and says Hypoid 90 certified. I also bought a oil pump to pump it in.

the issue is i have seen numerous comments that say you need to pump from the bottom plug to ensure no air gaps until it reaches the middle drain plug then start pumping from the middle until it reaches the top. But i have also seen some comments that say the only right way to do it on an OMC is to fill only from the middle, however everytime there was not a reason given for this method. Can someone explain why you should only pump from the middle drain plug and not bottom first? Or is this just wrong infomration being passed around? Thanks
 

Jake707

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Wouldn't filling from the middle allow possible air pockets that filling from the bottom would alleviate?
 

bruceb58

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Wouldn't filling from the middle allow possible air pockets that filling from the bottom would alleviate?

Nope. Filling from the bottom actually causes them. Do a search on here. There are a number of people that have wiped out their drives filling from the bottom.
 

Jake707

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Ok. Thanks for the info. Hopefully my pump is in today and I'll knock it out after work. Here's a picture of the fluid I bought. This should be good right? The gal at the store said it is what they use but since it's an old OMC I'm just cautious.
 

Jake707

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And the hits just keep on coming..... Just got out there and pulled the drain plug. After about 10 seconds of straight water coming out I finally started to get some oily sludge coming out. The drain plug and the middle full plug didn't have I rings on them but they were really tight so I duo by it was getting into the drive from there. Where should I look next? Should I run water through the full plug to flush out the sludge or just pump the new gear oil in?
 

bruceb58

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The rings need to be changed every time you change the gear lube.

I would do a pressure test on it to make sure it wasn't a seal that let the water in although if the plugs didn't have gaskets on them, that may be the cause.

DO NOT put water in there. Maybe diesel fuel to flush it out. The problem you have now is what kind of corrosion do you have on the gears and bearings?Worst case, it eventually goes out and you buy a SEI drive or a used Cobra drive.
 

Jake707

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I put new o rings on the drain plugs and pumped about half a quart or so of new fluid from the top until I got clean fluid coming out of the bottom plug. Then I filled it up until the fluid was at the line on the dipstick. I'm taking it out tomorrow so I will pull the plug after and see if more water is in there. If so then I have a bad feeling that the next step is to pull the drive and replace all the seals.
 

HT32BSX115

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I put new o rings on the drain plugs and pumped about half a quart or so of new fluid from the top until I got clean fluid coming out of the bottom plug. Then I filled it up until the fluid was at the line on the dipstick.

Howdy,


If you filled it from the top, DON'T run it. You may damage or destroy the drive.........If you continued filling it from the "fill" port, ENSURE that you filled it with the correct amount. The Big (King Kobra) drive held 108oz of oil for example. One model held 64oz if remember correctly.

There'd be nothing wrong with pouring in some diesel mixed with clean motor oil, and running the drive ON THE TRAILER to emulsify the remaining water. Then you could drain it.

You don't want water in there because it can increase the pressure in the drive when the drive (and oil) heats up.

According to the OMC manual, you fill it "to the line" with the dipstick "resting on top of the threads to allow for a slight overfill". THEN subsequent level checks are accomplished with the dipstick screwed all the way in.

I am with Bruce though. I would pressure check it!
 

Jake707

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Does that check for issues other than a bad seal? Can that be done if I remove the drive and bring it to a shop or does it need to be on the boat?
 

Jake707

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Sorry. Just to clarify I filled it from the top drain plug meaning the plug in the middle. Not the top where the dip stick is.
 

HT32BSX115

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Does that check for issues other than a bad seal? Can that be done if I remove the drive and bring it to a shop or does it need to be on the boat?

A shop can pressure and vacuum check a drive easily. I think there's instructions in the "stickies" for pressure checking a drive.

You simply pump it up so see if it'll hold approx 10 psi or so.

Here's an example
 

Jake707

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I just got home from the lake after a full day of use. I will put the trim down and drain it tomorrow to see what is in there and let you know.
 

Jake707

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I didn't replace all of the I rings no. Just the bottom drain plug one. I just drained the oil and it was a little blackish sludgy at first then turn green. It looks like maybe a little bit of water did still get in there or it could be it still had some sludge built up from before. I'm going get two more bottles of fluid tomorrow and fill it back up. Ill shop around and see if I can get some more I rings and replace them all. One website had them for $5 but another $25 for shipping. So I'll look elsewhere.
 

bruceb58

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Go to a dealer. They are cheap. Don't put it in the water again until you do. You should be doing a pressure test.

Not sure why you aren't following our advice.
 
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