Oil change on a '78 50HP Merc Outboard

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Bigbird99

Recruit
Joined
Jul 10, 2010
Messages
3
I only have a generic repair manual for older Merc outboards but I need to find out where the two screws are (one in and one for air) to change the gear oil in my '78 50Hp Merc on the leg. I only see one screw and I've removed the prop to see if there are any screws inside but don't see any. So, where does the gear oil go?

Any help at all would be most appreciated.


Scott
 
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Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,814
Re: Oil change on a '78 50HP Merc Outboard

There should be one plug in the front of the gearcase, next to the very start of the skeg. The other is on the side of the gearcase, just above the antiventilation plate.
 
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Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,814
Re: Oil change on a '78 50HP Merc Outboard

You will likely need a hand impact driver to remove and tighten the vent(top) and fill (bottom) screws. Remove them and let the gear oil drip into a pan. Now buy a quart of any marine gear oil for mechanical shift motors, and pump or squeeze it into the bottom hole. When it emerges from the top hole, install the top plug with a new gasket. Now remove the gear lube source and insert the lower plug, with a new gasket. Tighten securely.
 
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