You don’t have to take out the water tube. just put in the 5" extention. I had a tool to hammer into a copper tube to expand it so it would slip over the water tube to make the 5" extension. The factory uses an "O" ring to seal the extension, I used solder. The only water tube extension I can come up with is for the Evinrude Big Twin. I believe the 18 is a smaller diameter. . . 🙄
