1977 Johnson 4 HP Vent Screw?

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johnitahoe

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I have a 1977 Johnson 4 HP. I found the screw to put gear oil in the lower unit but I can't find a vent screw. There is a hole where you would expect the vent screw to be, but I can't tell if a vent screw goes in there or what size it would be?
 
johnitahoe said:
I have a 1977 Johnson 4 HP. I found the screw to put gear oil in the lower unit but I can't find a vent screw. There is a hole where you would expect the vent screw to be, but I can't tell if a vent screw goes in there or what size it would be?

I worked on one of these last year and IIRC it does not have one.

Put it on its side with the top of the hole level with the floor and fill leaving an air bubble equal to a teaspoon/tablespoon for expansion and you should be good.
 
The gearcase diagram looks similar to my 69 Evinrude 1.5. No second plug as best as I can tell. I followed similar steps that RaisedByWolves laid out.
Also in this video, he drains the oil with one plug only. https://www.youtube.com/watch?v=BVF-Rno42dA
 

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