How to replace lower unit grease on 1991 OMC Cobra 4.3

Ski Bob

Seaman Apprentice
Joined
Jul 20, 2013
Messages
31
Ok, I was jsut hoping for a quick reply. I noticed a guy a few threads down replaced the lower unit grease on his 4.3 Cobra and toasted his drive. He referred to draining it from the bottom and filling it from the bottom and it failed in five minutes.

According to my book, there are THREE screws on the starboard side for the lower unit grease draining and filling. The bottom drain by the skeg, the middle VENT and the top dip stick.

I open the top dip stick to get air and the bottom drain to drain it. Then, instead of the vent, I screw the little pump for filling it into the drain by the skeg and pump the thing full. The unit calls for 64 ounces and I make darn sure I pump 64 ounces into it.

So, am I risking anything pumping from the bottom instead of filling from the vent in the middle of the drive? Heck, when I'm done, the gear oil registers exactly full on the little dip stick so how can a guy go wrong? Unless it's me. Thanks, Bob
 

Sparkinator

Chief Petty Officer
Joined
Aug 15, 2009
Messages
423
Re: How to replace lower unit grease on 1991 OMC Cobra 4.3

The sticky for MUST READ for DIY on this OMC forum main page has the proceedure for filling an OMC drive. I think it has the pictures as well.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,923
Re: How to replace lower unit grease on 1991 OMC Cobra 4.3

MUST be filled from the side. There is an air pocket that doesn't get filled when filled from the bottom.
Get a manual. Then READ it. Unless you got lots of $$$$
 

Ski Bob

Seaman Apprentice
Joined
Jul 20, 2013
Messages
31
Re: How to replace lower unit grease on 1991 OMC Cobra 4.3

And to think I never have any luck! Anybody interested in a Cobra Stern drive that has dodged every bullet known to man? I am going to replace drive in spring to Volvo Penta. Now just need to find the mechanic to do it and saveup money. So, in other words, I am going to drain the darn thing again and re-fill it from the side because now that I know, sure as SH_T this thing will fry! Thanks again.
 
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