If any of you have run into this problem I have a solution. Mercruiser discontinued the fuel rail crossover o-rings from their inventory. I rebuilt my engine but because of 8 o-rings I couldn't finish the job. Luckly, I'm in the rubber business so I sourced the o-rings from Apple Rubber in MA. The o-Rings are Viton, Flourocarbon rubber 1/4" ID, 1/2" OD and 1/8" thick. Mercruiser was no help so the hell with them and their engines. Glad I could help someone.