Dove into my 150SX Yamaha last night to replace the water pump. It had gotten to where it wouldn't cool at idle RPM. Dropped the lower unit no problems. Housing, no problem. Plastic collar that is usually a problem? No problem. Get the impeller of the drive shaft, and the problem rears it's ugly little head. Looks like the woodruff key that was used last time is soft cast iron. Badly rusted and soft as a pancake. Couple of taps with the hammer and it already started to flatten out. Tried direct heat, hammer and punch from the top to no avail. Going to get a small diameter cutoff wheel for the dremel and try to slit it longways. It's been soaking in Breakfree since last night.