I need help? I have a 98' 175 Merc efi and to help save money I wanted to change the lower unit oil my self.

I was told that it would take 2 plus quarts. I drained the unit and when I went to fill it (using a pump through the bottom plug) could only get about 24 oz in it. Any help with this will be greatly appriciated. Also can the lower unit be flushed with trans fluid or something else to clean it?

There is no way it will hold 1/2 gal of fluid. If you pumped it in from the bottom and it ran out the top you are good to go.

I have a 225 Merc and it takes less than a qt. to fill it.

When filling the LU on a Merc, remove both upper vent plugs.  Fill till the forward vent starts overflowing, replace the plug, then fill till the rear vent overflows.

My 90 is supposed to hold 22 oz., I got about 19 oz. in it.