CONTINUOUSWAVE

I have a 2014 Mercury four stroke 40 hp on my new to me 13 super sport. Just changed the gearcase oil for the first time. I have done this many times before but first time with this engine. Got engine in vertical position. The lower unit has typical drain fill plug and two top vent plugs. Started engine and ran for 15 minutes in gear to warm gear oil, drained for 10 min to a very slow drip, then started filling. After oil came out vent hole I installed plug and kept pumping till it came out second vent hole and replaced that plug. In total I put in maybe 8-9 oz. Owners manual says 14.9 oz???

Not only that but the owners manual was calling fill plug the vent plug, and the vent plug the drain plug. It also only showed one vent plug and there are two???

Thoughts anyone please!!!

What was the condition of the oil you drained? If emulsified with water it can thicken up and leave a gooey residue inside the gear case which would keep all of it from draining out. Otherwise the only thing else I could suggest is to run it again and drain and refill. Maybe you need to tilt the engine away from exactly vertical and then back to get most of it out. Good luck.

I have a larger 60HP Merc but the instruction call for having the motor tilted at a 60 degree or so angle from vertical. Together with the comment Robert made that might be it.