It’s just about all been said. Agreed, you need the proper recoil. You also need the 3 balls that lie in the cup. They are just standard ball bearings, but I’m not totally sure what size.

The exhaust is cooled by a ram tube that you will see behind the prop. There is no water pump on this one. The propeller rams water into the tube, along with forward motion through the water. Good system on the lake, but they don’t work real well in a barrel.

Those are one of the only air cooled outboards that I have much love for. They do work well. Salt water is rough on them because it is blowing salt air down across everything.