After installing water pump kit, I had two o-rings left. I discovered that they were for a impeller housing spacer which my motor did not have. I double checked to ensure in was not hiding up in motor. This motor was operating fine for 10 years without the spacer. I bought a new spacer, Part # 326692 (plastic). On the marineengine.com site the plastic spacer is stated as obsolete. This part is now made of metal not plastic. My questions: Is this part really needed? If so, Should I install a metal spacer instead of the plastic one. Just not sure why the part is obsolete.