yamaha water pump ?

[Geekie1]

Spareparts is right! I have an earlier Yamaha 150 but the water pump assembly on mine looks like your first picture. The metal housing with the tab on top slides into the plastic outer water pump housing. The tab keeps the metal insert from spinning inside of the outer plastic housing by the impeller turning. The large O-Ring is inserted into the bottom of the outer water pump plastic housing and seals the bottom of the plastic housing and the bottom plate. The smaller O-Ring goes between the outer plastic housing and the inner metal housing to seal the top of the pump by the drive shaft. My water pump repair kit is the Yamaha OEM kit from www.boats.net I'm not sure if this explanation is what you are looking for or if it is understandable but maybe it will help.

Geek