Converting evinrude short shaft to long shaft

[Don A.]

I'm converting a 8 HP short shaft evinrude to a long shaft. The extension water tube that came in the kit has an internal O-ring that is supposed to slip over the existing water tube. I can't get the extension tube and O ring to slip over the existing tube. The O-ring looks too big to fit in the extension tube and ends up getting pushed down the tube when I try to slip it on the receiving tube. The parts are evinrude parts. Any hints on this?