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1979 5hp gear oil change??

R

rick465

Member
Hey, I have a '79 Merc 5hp (4.5actually) s/n 5271800 that has to have a gear oil change. The problem is that I can only find 1 screw. It is on the starboard side, right above the cavitation plate. There is nothing between that and the top of the shaft or that and the bottom of the shaft. My guess is that it is the drain screw. Where is the vent screw???
Any hints?
If you need more info, let me know and I'll see what I can do.

THANKS!!!1.jpg2.jpg
 
There is the small vent under the cavitation plate, which I assume is the water intake. Directly behind that vent is a nut that is used to hold the lower unit on. Behind the nut, just at the end of the cavitation plate is a threaded hole that presumably held the anode.
I don't see any other screw. 3.jpg
 
I understand. As you can see from the first pic there IS a screw just above the cavitation plate. It is a small screw and would not fit any normal 'pump' type apparatus or other method for putting in gear oil, other than a syringe. There is no screw below that one to fill the motor from. ...and IF the screw that is there in pic 1 IS the fill screw then there is no vent screw above it. There just has to be 2, right??
 
HOLY CRAP! I FOUND IT!
The small screw above the cavitation plate IS the vent screw. The drain/fill screw is in the front of the bullet just offset to the lower starboard side. Hard to see and not really a place you would look.
THANKS for the help! Thinking through the issue was just the thing.

Hope this helps some other poor miscreant like me someday.
 
????----That is the vent screw !----You FILL that gearcase from the bottom till oil comes out that vent hole.-----There is no other way to fill that gear case.----Motor must be in the normal running position !-----Make sure you understand how to fill this lower unit.---Mistakes will cost you money.----Watch a few U-tuber videos and see how it is done !!
 
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