Lower unit oil change 6 Horse Evinrude

jeepwm69

Petty Officer 3rd Class
Joined
May 26, 2010
Messages
84
I read the sticky on changing the lower unit oil. My question is regarding filling the unit through the "drain/ fill hole". I assume the motor is sitting upright during this procedure, so I'm wondering why you wouldn't pop the top and bottom plugs out, allowing the oil to drain the bottom hole, and then put the drain plug back in and fill through the vent hole until it's full (similar to my manual transmissions/ transfer cases on my Jeeps)? What am I missing here? Why do you fill through the bottom hole until the level reaches the top hole?
 

BF

Lieutenant
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Apr 8, 2003
Messages
1,489
Re: Lower unit oil change 6 Horse Evinrude

done that way so the thick oil can push the air up and out of the vent hole to completely fill the LU. If you fill from the top, air has to push it's way up through the gear oil... this oil is thick enough that the lower unit won't "burb" all the air out trapped and therefore leave you with a 1/2 filled LU and bearing failure... Get one of the pumps that screws into the bottom hole, best few bucks you'll ever spend. Then pump until oil comes out the vent hole. And replace the gaskets on the screws...

Oh, and yes motor should be down for this (anti-ventilation plate parallel to the ground). Otherwise air can get trapped in the bearing carrier... again leading to underfilling...

hope this helps!
 

hidef

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Aug 22, 2009
Messages
1,465
Re: Lower unit oil change 6 Horse Evinrude

You actually get a quicker fill. You can squeeze the bottle and force the oil up or use a pump. I prefer the pump myself. You know when the L/U is filled and the little bit that leaks out as you put the plugs back in is very minimal. You do the vent first and then the drain plug.
 

BF

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Joined
Apr 8, 2003
Messages
1,489
Re: Lower unit oil change 6 Horse Evinrude

Oh, and I saw your other thread about the carb work... since this is a new to you motor that you're bringing back into service, I'd highly recommend replacing the water pump impeller while you're at it. It would be a shame to toast the motor b/c of a few dollar rubber part! Good luck, these are great little motors.
 

jeepwm69

Petty Officer 3rd Class
Joined
May 26, 2010
Messages
84
Re: Lower unit oil change 6 Horse Evinrude

Just did the water pump, rebuilt the carb, new fuel pump, and got a new pull rope on it. Runs like a top now and is peeing water great. Going to change the lower gear oil and call it good for another 40 years.

Thanks for the input!
 
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