With the combination of first off being messy, and secondly not being able to get all the oil out, because of the engine tilt. Every time I change oil there is approx. a quart that can't be removed via the dip stick. I would like to put a drain plug in the back of the oil pan on a Yanmar 3GM. The thought is to remove the oil pan, and drill and tap a fitting at the rear. Then install a small electric pump, which would be much less messy, and would get all the oil out. I know the pan is cast aluminum, but have no idea of how thick the material is. Has anyone ever done this, or does anyone know if the pan material is thick enough, or strong enough to hold a fitting like this, without a danger of cracking or breaking or leaking. My thinking is to just attach a threaded "L", possibly using something like Marine Tex or other epoxy to reinforce it, and go with tubing from there, not having much weight on the pan itself. As usual, any thoughts, ideas or suggestions greatly appreciated.