I have a 2011 T25 Yamaha. Installed a Seara water pump kit, after much aggravation found it did not fit. The key way is about twice as fat as original so I used the original but did not take notice that the ID of Seara impeller was about 1/32 larger than OEM which allowed the key to slip. The original should fit snugly on the shaft where it rides. Pay extra for a OEM part and save the hassle.
Regards
Bob
Regards
Bob