1984 evinrude 150hp. Changing the lower unit oil and i was only able to get about 13 ounces removed. Motor was in down position. I was surprised at that amount. I knew it should have been more. Researched it and it is supposed to hold 28 ounces. I took an air nozzle to the vent hole and was unable to get much more out.
Thinking maybe it was low to begin with i filled it up with fresh oil. It was only able to hold 13oz. Why would the volume be off by half? No water in oil or metal shavings?
Boat has sat for about a year of that helps?

If you fill it from the bottom until it comes out of the top hole, it's full. I'm not sure about the 13 vs 28oz. I wonder if you're looking at the correct lower unit spec. There's not more in there than the prop shaft and gears.
Good luck

I had to fill from the top with a pump type oil can until it overflowed. The 28 oz number came straight from the service manual.

If you filled from the top you probably have air in there.

While you are referencing that service manual, you should read how to install that lubricant. There are two holes because the system is air-tight, or should be, at least. You "air-lock" and limit what can be injected if you use the top hole. This is lower unit service 101.

Yes, you are correct. Yes, i am aware of correct filling procedure. The pump i bought doesn't fit my lower drain plug. I am going to have to find one that does. Trying to wrap up last of the of the maintenance on it i just used what i had. Regardless, only 13 ounces drained out and only 13 oz was all it would hold filling up.

all the drain and xfill plug threads are the same except yamahas. if threads are different its been southern engineered

Even if it doesn't fit, stick it in there and push it in from the bottom. It's so thick that you'll entrap air in there when filling from the top. It's thick enough that you won't lose much once it comes out the top (if you plug up the top), you can then plug the bottom.
Tim

That's what i thought as well. The plastic piece that threads in to the lower unit is way to big. I bought a new pump that comes with the Yamaha adapter. The Yamaha adapter is a little to big as well.

I will probably try what you are suggesting. Mainly because the manual says 28.3oz and I'm at half that capacity. I was hoping another member here had the same experience with these now "antique" motors lol

If you’re going to own this motor, you can pick up the pump head at academy for under $10 that will screw into your motor’s lower unit. It’s worth it. Until then, you can force fit it.
Tim