Catalina 350 International Association

My Diesel fill cap needs a new O-ring...I was able to find 1 1/2" O-rings for the two water fill caps, but the one on the diesel fill cap while also 1 1/2" requires a thicker O-ring that I haven't been able to locate. Has anyone found a replacement for this O-ring?

You might try https://www.theoringstore.com/ I used them to get a replacement O ring for the raw water strainer.

I used an O-Ring kit for making just about any size needed. Came with lengths of rubber, different diameters. You cut to length and glue ends together. Might not be perfect for high pressure but good for fill caps.