Omc cobra outdrive gear oil change

[Hildebrand]

Hi, I have read up on this but still wasn’t clear on some things. I want to change the gear oil in my outdrive, 5.8 omc. I know of the three plugs in the drive and I need to lower the drive and drain it out the bottom. Can I just add 80-90 w Marine gear lube from the top? I’ve seen a video where a guy does it from the bottom and one guy does it from the second plug. Any input would be awesome. Thank you

 

[Scott Danforth]

no, you need to follow the steps and fill from the bottom or risk burning up your drive.

see the stickies at the top of the OMC forum

 

[Big Gee]

no, you need to follow the steps and fill from the bottom or risk burning up your drive.

see the stickies at the top of the OMC forum

This is critical to follow! Otherwise there's a risk of trapping air in it.

 

[HT32BSX115]

Hi, I have read up on this but still wasn’t clear on some things. I want to change the gear oil in my outdrive, 5.8 omc. I know of the three plugs in the drive and I need to lower the drive and drain it out the bottom. Can I just add 80-90 w Marine gear lube from the top? I’ve seen a video where a guy does it from the bottom and one guy does it from the second plug. Any input would be awesome. Thank you

Howdy,

Please post the year/model number of your engine/drive package.

If this is a Dog-Clutch Cobra, You MUST Fill it from the [MIDDLE] "fill port" and that is NOT the bottom drain port.

If you fill it any other way, you risk destroying the drive because of a bubble that will be trapped inside and will uncover the upper gears after running a very short time.

DO NOT DO NOT DO NOT fill it from the bottom!



Cheers,


Rick

 

[Lou C]

On the crowley marine website there is a tech support page that shows you exactly how to do it, it's all taken from the factory shop manual.
I've been doing it that way over 15 years and never had a problem!

 

[HT32BSX115]

On the crowley marine website there is a tech support page that shows you exactly how to do it, it's all taken from the factory shop manual.
I've been doing it that way over 15 years and never had a problem!

As always, Lou is "Spot-On"......that Crowley Marine manual excerpt is an excellent resource :thumb:

There are people who say they've filled them from "Bottom" drain plug........BUT ONLY with the "FILL" port OPEN.

When filling that way, they wait until they see oil appear at the "FILL" port and then stop, close the drain port and then fill the rest of the way from the fill port.

While this may "work" just fine, it is NOT in accordance with the OEM OMC service manual for a Dog-Clutch Cobra......AND there's no reason to do it that way. The Service manual is quite clear. placing the dipstick on top of the threads when filling from the "FILL" port allows for a slight "overfill" to ensure any small bubbles are accommodated when the oil warms up.

Note that they do suggest "topping off" after initial filling by pouring/pumping oil in through the dipstick port. (understand, we're only talking about a fraction of a cup to top-off.)

 

[Hildebrand]

It’s a 1990 four Winn’s sundowner, with a 5.8 omc.
I did it the way the sticky showed. I drained from the bottom with the top open and after it drained I put the bottom plug back in and filled from the middle plug until I had a good reading up top, pulled the house and closed it back up.
Me being a rockie with boats, I only bought 64 oz of gear lube from the marina but when I did it I lost some in the process. I was a touch low so I went to the local auto parts store and bought some 80-90 gear lube, will that be fine to add or does it have to be the exact one I got at the marina ? Thanks agin

 

[HT32BSX115]

I only bought 64 oz of gear lube from the marina but when I did it I lost some in the process. I was a touch low so I went to the local auto parts store and bought some 80-90 gear lube, will that be fine to add or does it have to be the exact one I got at the marina ? Thanks agin

Nah, you did good! :thumb:

Your question brings up another point about gear lube. The NMMA doesn't specify a "Marine" gear lubricant standard (like FC-W motor oil or 2-stroke oil etc. )

So any standard NON-LS [limited slip] gear lubricant is going to be fine. Most of us like Synthetic 75W-90 gear lube but all of the non-syns are ok too.

Just change it at the end of the season or at least drain some to check for water intrusion if it did leak so you don't have water in there for the entire winter........

 

[Lou C]

Yep, I do use the Merc High Performance gear lube, but because one time when I had a bad seal leak, I had so much water in the drive it spurted out of the dipstick hole when I went to check it! This was a long time ago, like in 2005 or so, that was the last time I had it resealed. Anyway, I think the 'marine' gear oils may do better if you have a bit of water in the oil, at least that's what they use to sell em, not sure if there is really truth to it or not but I keep using it....

 

[HT32BSX115]

Anyway, I think the 'marine' gear oils may do better if you have a bit of water in the oil, at least that's what they use to sell em, not sure if there is really truth to it or not but I keep using it....

They absolutely do make that "claim"!

However, "truth be known" .....The ASTM standard for testing gear lubricants include a test for up to 10% water intrusion.

"Marine" lubricant retailers like to claim their oil can handle up to 10% water...... but in fact, virtually all gear lubricants are tested to this standard.

 

[bruceb58]

Also, make sure you always change the o-rings or gaskets on all 3 plugs every time you change your gear oil.

 

[Hildebrand]

Thanks agin for all your time. I think I’m all set on the drive. I’ll get it out this week and hope all is good.

 

[james-Z]

can i use valvoline 80/90 gear oil in a omc cobra out drive? or does it have to be quicksilver or other marine lube/