Re: 93 johnson 115hp lower unit oil change
The recommended oil is 80-90 outboard gear oil, it has additives to protect the lower if you have water intrusion. I personally use BRP's synthetic brand. A pump like the following will make things much easier, not to mention cleaner.
As you said, put a catch bin beneath the lu, drain all fluid. Screw in the adaptor that comes with the pump into the drain hole, then pump it until oil exits via the vent hole. Install vent screw with new crush washer, remove pump from drain hole, then install drain screw with new crush washer. The washers will be available at your dealer, just grab a bag of them so you always have them on hand, they are cheap. They are to be used only once, so replace them whenever you remove the drain or vent screw. Job done.
Just ensure that you do not notice any milky white oil exit, which is a sign of water intrusion into the lu. Also note the metal flakes on the magnet on the drain screw, any large ones and you may have internal issues.
Sorry I type slowwww
