Re: Switching out wrong oil in the lower end
There are two screw-in plugs on the starboard side of the lowere unit. One is right at the bottom and the other is just below the cavitiation plate. When you remove the bottom one oil will dribble out so remove the top also to allow it to completely drain.
The manual says to fill through the bottom hole with a pump and when the oil starts to flow from the top hole the unit is full. Replace the top plug first ensuring the gasket is good. Now remove the pump and replace the bottom plug before the oil leaks out.
The first time I changed the oil, I didn't have a pump, so after draining the old oil I fillled from the top, replace the plugs, ran for a minute on the muffs, then topped up from the top again. That worked for me. I have the pump now and I use that.
My 50173s would not shift into reverse until I changed out the oil. Could have been the wrong oil in it or could have been gummed up from sitting a long time. Don't know but is has worked fine for two years now with no problems. Good little motor. Good luck with yours.
