Change lower unit oil.

H

hockey22

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Mar 30, 2005
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I have a 90 Merc and I need to know when I change the lower unit oil, do I take out the vent plug, or the oil fill plug? I know how to change the oil, just need to know what plug to take out.<br /><br />Thanks
 
Silvertip

Silvertip

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Sep 22, 2003
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28,771
Re: Change lower unit oil.

You need to remove both plugs. When fully drained, you refill the lower unit through the lower drain plug until lub comes out the vent. Install the vent plug first, then drain plug.
 
H

hockey22

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Re: Change lower unit oil.

I have two plugs on the top and one on the bottom. I know that the one the bottom has to come out. But is the top the vent plug, or oil fill plug?<br />Thanks
 
1

1968_Red_fish_IMP

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Feb 23, 2005
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31
Re: Change lower unit oil.

Should be indented into the unit next to the vent plug (vent). If you have 2 at the top, one a bit larger and the other smaller, the smallest is the vent plug and the largest is the waterpump "flush" plug. Take out the drain plug at the bottom, and remove the vent plug. Buy a gear oil pump kit at wal mart (about $7.00) and it screws onto the quart bottle of gear oil and also threads into the drain plug hole. Fill by pumping till the oil comes out the vent plug hole, this removes all air from the gear case.
 
Vlad D Impeller

Vlad D Impeller

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2,644
Re: Change lower unit oil.

the drain plug is the oil fill plug, the lube is pumped in from the bottom like Upinsmoke said.
 
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